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	$62.27	7.819%	$67.1389	$67.14	$67.15	$67.10
Purchase #2	$194.62	11.393%	$216.7931	$216.79	$216.80	$216.80
Purchase #3	$50.87	3.570%	$52.6861	$52.69	$52.70	$52.70
Purchase #4	$78.94	13.313%	$89.4493	$89.45	$89.45	$89.40
Purchase #5	$195.45	3.251%	$201.8041	$201.80	$201.80	$201.80
Purchase #6	$124.39	5.371%	$131.071	$131.07	$131.05	$131.10
Purchase #7	$242.83	3.199%	$250.5981	$250.60	$250.60	$250.60
7 purchase totals =	$949.37		$1,009.5406	$1,009.54	$1,009.55	$1,009.50