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	$246.85	6.210%	$262.1794	$262.18	$262.20	$262.20
Purchase #2	$110.89	7.250%	$118.9295	$118.93	$118.95	$118.90
Purchase #3	$227.78	4.851%	$238.8296	$238.83	$238.85	$238.80
Purchase #4	$244.93	9.731%	$268.7641	$268.76	$268.75	$268.80
Purchase #5	$58.83	10.683%	$65.1148	$65.11	$65.10	$65.10
Purchase #6	$101.55	7.510%	$109.1764	$109.18	$109.20	$109.20
Purchase #7	$171.69	12.707%	$193.5066	$193.51	$193.50	$193.50
7 purchase totals =	$1,162.52		$1,256.5004	$1,256.50	$1,256.55	$1,256.50