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	$127.85	3.200%	$131.9412	$131.94	$131.95	$131.90
Purchase #2	$235.91	7.820%	$254.3582	$254.36	$254.35	$254.40
Purchase #3	$108.27	8.379%	$117.3419	$117.34	$117.35	$117.30
Purchase #4	$124.68	9.271%	$136.2391	$136.24	$136.25	$136.20
Purchase #5	$99.85	11.407%	$111.2399	$111.24	$111.25	$111.20
Purchase #6	$114.89	8.166%	$124.2719	$124.27	$124.25	$124.30
Purchase #7	$184.51	13.405%	$209.2436	$209.24	$209.25	$209.20
7 purchase totals =	$995.96		$1,084.6358	$1,084.63	$1,084.65	$1,084.50