Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$224.40	12.769%	$253.0536	$253.05	$253.05	$253.10
Purchase #2	$218.46	12.263%	$245.2497	$245.25	$245.25	$245.20
Purchase #3	$126.72	11.764%	$141.6273	$141.63	$141.65	$141.60
Purchase #4	$150.32	10.475%	$166.066	$166.07	$166.05	$166.10
Purchase #5	$101.30	4.503%	$105.8615	$105.86	$105.85	$105.90
Purchase #6	$190.86	5.395%	$201.1569	$201.16	$201.15	$201.20
Purchase #7	$113.77	11.665%	$127.0413	$127.04	$127.05	$127.00
7 purchase totals =	$1,125.83		$1,240.0563	$1,240.06	$1,240.05	$1,240.10