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	$249.86	10.378%	$275.7905	$275.79	$275.80	$275.80
Purchase #2	$152.86	6.594%	$162.9396	$162.94	$162.95	$162.90
Purchase #3	$14.55	5.165%	$15.3015	$15.30	$15.30	$15.30
Purchase #4	$100.28	8.244%	$108.5471	$108.55	$108.55	$108.50
Purchase #5	$172.50	10.744%	$191.0334	$191.03	$191.05	$191.00
Purchase #6	$184.74	6.580%	$196.8959	$196.90	$196.90	$196.90
Purchase #7	$161.41	7.834%	$174.0549	$174.05	$174.05	$174.10
7 purchase totals =	$1,036.20		$1,124.5629	$1,124.56	$1,124.60	$1,124.50