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	$101.80	6.162%	$108.0729	$108.07	$108.05	$108.10
Purchase #2	$240.28	13.746%	$273.3089	$273.31	$273.30	$273.30
Purchase #3	$67.51	5.256%	$71.0583	$71.06	$71.05	$71.10
Purchase #4	$90.97	10.849%	$100.8393	$100.84	$100.85	$100.80
Purchase #5	$245.93	6.138%	$261.0252	$261.03	$261.05	$261.00
Purchase #6	$50.48	13.450%	$57.2696	$57.27	$57.25	$57.30
Purchase #7	$216.54	10.708%	$239.7271	$239.73	$239.75	$239.70
7 purchase totals =	$1,013.51		$1,111.3013	$1,111.31	$1,111.30	$1,111.30