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	$92.69	4.607%	$96.9602	$96.96	$96.95	$97.00
Purchase #2	$216.97	12.634%	$244.382	$244.38	$244.40	$244.40
Purchase #3	$218.87	5.373%	$230.6299	$230.63	$230.65	$230.60
Purchase #4	$56.46	11.199%	$62.783	$62.78	$62.80	$62.80
Purchase #5	$92.90	7.510%	$99.8768	$99.88	$99.90	$99.90
Purchase #6	$153.41	3.186%	$158.2976	$158.30	$158.30	$158.30
Purchase #7	$36.54	5.171%	$38.4295	$38.43	$38.45	$38.40
7 purchase totals =	$867.84		$931.3590	$931.36	$931.45	$931.40