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	$48.55	9.354%	$53.0914	$53.09	$53.10	$53.10
Purchase #2	$41.61	11.256%	$46.2936	$46.29	$46.30	$46.30
Purchase #3	$166.81	13.199%	$188.8273	$188.83	$188.85	$188.80
Purchase #4	$179.36	11.760%	$200.4527	$200.45	$200.45	$200.50
Purchase #5	$216.45	8.535%	$234.924	$234.92	$234.90	$234.90
Purchase #6	$100.98	13.851%	$114.9667	$114.97	$114.95	$115.00
Purchase #7	$234.85	4.136%	$244.5634	$244.56	$244.55	$244.60
7 purchase totals =	$988.61		$1,083.1191	$1,083.11	$1,083.10	$1,083.20