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	$58.82	9.588%	$64.4597	$64.46	$64.45	$64.50
Purchase #2	$152.98	13.696%	$173.9321	$173.93	$173.95	$173.90
Purchase #3	$181.59	3.772%	$188.4396	$188.44	$188.45	$188.40
Purchase #4	$214.51	11.282%	$238.711	$238.71	$238.70	$238.70
Purchase #5	$86.27	3.690%	$89.4534	$89.45	$89.45	$89.50
Purchase #6	$36.81	9.281%	$40.2263	$40.23	$40.25	$40.20
Purchase #7	$218.99	9.837%	$240.532	$240.53	$240.55	$240.50
7 purchase totals =	$949.97		$1,035.7541	$1,035.75	$1,035.80	$1,035.70