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	$74.84	11.109%	$83.154	$83.15	$83.15	$83.20
Purchase #2	$248.82	5.766%	$263.167	$263.17	$263.15	$263.20
Purchase #3	$53.83	13.354%	$61.0185	$61.02	$61.00	$61.00
Purchase #4	$48.94	12.612%	$55.1123	$55.11	$55.10	$55.10
Purchase #5	$173.89	13.276%	$196.9756	$196.98	$197.00	$197.00
Purchase #6	$170.77	12.831%	$192.6815	$192.68	$192.70	$192.70
Purchase #7	$146.80	13.270%	$166.2804	$166.28	$166.30	$166.30
7 purchase totals =	$917.89		$1,018.3893	$1,018.39	$1,018.40	$1,018.50