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	$49.81	9.314%	$54.4493	$54.45	$54.45	$54.40
Purchase #2	$182.37	8.740%	$198.3091	$198.31	$198.30	$198.30
Purchase #3	$40.92	4.503%	$42.7626	$42.76	$42.75	$42.80
Purchase #4	$194.62	7.462%	$209.1425	$209.14	$209.15	$209.10
Purchase #5	$239.63	3.604%	$248.2663	$248.27	$248.25	$248.30
Purchase #6	$139.36	5.348%	$146.813	$146.81	$146.80	$146.80
Purchase #7	$238.72	3.823%	$247.8463	$247.85	$247.85	$247.80
7 purchase totals =	$1,085.43		$1,147.5891	$1,147.59	$1,147.55	$1,147.50