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	$165.26	4.331%	$172.4174	$172.42	$172.40	$172.40
Purchase #2	$51.85	13.640%	$58.9223	$58.92	$58.90	$58.90
Purchase #3	$58.88	10.566%	$65.1013	$65.10	$65.10	$65.10
Purchase #4	$98.51	12.814%	$111.1331	$111.13	$111.15	$111.10
Purchase #5	$16.98	9.607%	$18.6113	$18.61	$18.60	$18.60
Purchase #6	$24.33	4.109%	$25.3297	$25.33	$25.35	$25.30
Purchase #7	$189.63	6.588%	$202.1228	$202.12	$202.10	$202.10
7 purchase totals =	$605.44		$653.6379	$653.63	$653.60	$653.50