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	$86.94	11.501%	$96.939	$96.94	$96.95	$96.90
Purchase #2	$170.93	8.269%	$185.0642	$185.06	$185.05	$185.10
Purchase #3	$109.57	8.369%	$118.7399	$118.74	$118.75	$118.70
Purchase #4	$32.36	11.565%	$36.1024	$36.10	$36.10	$36.10
Purchase #5	$155.93	6.504%	$166.0717	$166.07	$166.05	$166.10
Purchase #6	$94.55	6.223%	$100.4338	$100.43	$100.45	$100.40
Purchase #7	$103.90	7.450%	$111.6406	$111.64	$111.65	$111.60
7 purchase totals =	$754.18		$814.9916	$814.98	$815.00	$814.90