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	$141.42	11.389%	$157.5263	$157.53	$157.55	$157.50
Purchase #2	$52.25	5.588%	$55.1697	$55.17	$55.15	$55.20
Purchase #3	$239.39	12.399%	$269.072	$269.07	$269.05	$269.10
Purchase #4	$6.39	11.568%	$7.1292	$7.13	$7.15	$7.10
Purchase #5	$201.64	8.667%	$219.1161	$219.12	$219.10	$219.10
Purchase #6	$250.94	3.368%	$259.3917	$259.39	$259.40	$259.40
Purchase #7	$171.27	3.280%	$176.8877	$176.89	$176.90	$176.90
7 purchase totals =	$1,063.30		$1,144.2927	$1,144.30	$1,144.30	$1,144.30