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	$99.37	12.458%	$111.7495	$111.75	$111.75	$111.70
Purchase #2	$223.41	7.800%	$240.836	$240.84	$240.85	$240.80
Purchase #3	$250.93	13.728%	$285.3777	$285.38	$285.40	$285.40
Purchase #4	$222.74	9.237%	$243.3145	$243.31	$243.30	$243.30
Purchase #5	$74.89	11.386%	$83.417	$83.42	$83.40	$83.40
Purchase #6	$160.55	9.671%	$176.0768	$176.08	$176.10	$176.10
Purchase #7	$117.44	5.396%	$123.7771	$123.78	$123.80	$123.80
7 purchase totals =	$1,149.33		$1,264.5486	$1,264.56	$1,264.60	$1,264.50