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	$138.57	6.121%	$147.0519	$147.05	$147.05	$147.10
Purchase #2	$84.63	5.612%	$89.3794	$89.38	$89.40	$89.40
Purchase #3	$169.39	4.799%	$177.519	$177.52	$177.50	$177.50
Purchase #4	$32.80	10.591%	$36.2738	$36.27	$36.25	$36.30
Purchase #5	$91.97	9.231%	$100.4598	$100.46	$100.45	$100.50
Purchase #6	$9.69	4.538%	$10.1297	$10.13	$10.15	$10.10
Purchase #7	$178.99	7.447%	$192.3194	$192.32	$192.30	$192.30
7 purchase totals =	$706.04		$753.1330	$753.13	$753.10	$753.20