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	$77.33	7.756%	$83.3277	$83.33	$83.35	$83.30
Purchase #2	$182.69	11.546%	$203.7834	$203.78	$203.80	$203.80
Purchase #3	$118.44	5.233%	$124.638	$124.64	$124.65	$124.60
Purchase #4	$125.59	9.180%	$137.1192	$137.12	$137.10	$137.10
Purchase #5	$93.32	13.311%	$105.7418	$105.74	$105.75	$105.70
Purchase #6	$221.98	5.218%	$233.5629	$233.56	$233.55	$233.60
Purchase #7	$115.87	6.416%	$123.3042	$123.30	$123.30	$123.30
7 purchase totals =	$935.22		$1,011.4772	$1,011.47	$1,011.50	$1,011.40