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	$141.49	7.417%	$151.9843	$151.98	$152.00	$152.00
Purchase #2	$93.88	12.775%	$105.8732	$105.87	$105.85	$105.90
Purchase #3	$119.73	4.250%	$124.8185	$124.82	$124.80	$124.80
Purchase #4	$57.34	3.124%	$59.1313	$59.13	$59.15	$59.10
Purchase #5	$42.92	5.661%	$45.3497	$45.35	$45.35	$45.30
Purchase #6	$115.55	13.293%	$130.9101	$130.91	$130.90	$130.90
Purchase #7	$89.88	8.370%	$97.403	$97.40	$97.40	$97.40
7 purchase totals =	$660.79		$715.4701	$715.46	$715.45	$715.40