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	$185.66	5.681%	$196.2073	$196.21	$196.20	$196.20
Purchase #2	$141.74	5.398%	$149.3911	$149.39	$149.40	$149.40
Purchase #3	$60.49	10.382%	$66.7701	$66.77	$66.75	$66.80
Purchase #4	$68.66	4.688%	$71.8788	$71.88	$71.90	$71.90
Purchase #5	$34.41	7.572%	$37.0155	$37.02	$37.00	$37.00
Purchase #6	$91.76	3.716%	$95.1698	$95.17	$95.15	$95.20
Purchase #7	$183.76	4.694%	$192.3857	$192.39	$192.40	$192.40
7 purchase totals =	$766.48		$808.8183	$808.83	$808.80	$808.90