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	$60.28	8.347%	$65.3116	$65.31	$65.30	$65.30
Purchase #2	$90.35	6.523%	$96.2435	$96.24	$96.25	$96.20
Purchase #3	$147.57	12.416%	$165.8923	$165.89	$165.90	$165.90
Purchase #4	$173.98	13.143%	$196.8462	$196.85	$196.85	$196.80
Purchase #5	$25.74	12.319%	$28.9109	$28.91	$28.90	$28.90
Purchase #6	$7.68	7.340%	$8.2437	$8.24	$8.25	$8.20
Purchase #7	$89.47	7.414%	$96.1033	$96.10	$96.10	$96.10
7 purchase totals =	$595.07		$657.5515	$657.54	$657.55	$657.40