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	$120.62	4.872%	$126.4966	$126.50	$126.50	$126.50
Purchase #2	$212.52	4.755%	$222.6253	$222.63	$222.65	$222.60
Purchase #3	$53.61	9.446%	$58.674	$58.67	$58.65	$58.70
Purchase #4	$164.45	8.800%	$178.9216	$178.92	$178.90	$178.90
Purchase #5	$223.27	6.852%	$238.5685	$238.57	$238.55	$238.60
Purchase #6	$9.92	9.411%	$10.8536	$10.85	$10.85	$10.90
Purchase #7	$158.36	4.635%	$165.7	$165.70	$165.70	$165.70
7 purchase totals =	$942.75		$1,001.8396	$1,001.84	$1,001.80	$1,001.90