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	$68.98	5.564%	$72.818	$72.82	$72.80	$72.80
Purchase #2	$230.38	10.573%	$254.7381	$254.74	$254.75	$254.70
Purchase #3	$105.80	10.164%	$116.5535	$116.55	$116.55	$116.60
Purchase #4	$81.47	4.486%	$85.1247	$85.12	$85.10	$85.10
Purchase #5	$150.62	5.779%	$159.3243	$159.32	$159.30	$159.30
Purchase #6	$186.33	5.258%	$196.1272	$196.13	$196.15	$196.10
Purchase #7	$8.75	9.220%	$9.5568	$9.56	$9.55	$9.60
7 purchase totals =	$832.33		$894.2426	$894.24	$894.20	$894.20