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	$165.33	5.679%	$174.7191	$174.72	$174.70	$174.70
Purchase #2	$35.56	12.176%	$39.8898	$39.89	$39.90	$39.90
Purchase #3	$61.83	9.793%	$67.885	$67.89	$67.90	$67.90
Purchase #4	$32.72	8.367%	$35.4577	$35.46	$35.45	$35.50
Purchase #5	$196.50	8.216%	$212.6444	$212.64	$212.65	$212.60
Purchase #6	$221.35	4.143%	$230.5205	$230.52	$230.50	$230.50
Purchase #7	$219.54	13.254%	$248.6378	$248.64	$248.65	$248.60
7 purchase totals =	$932.83		$1,009.7543	$1,009.76	$1,009.75	$1,009.70