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	$152.45	9.233%	$166.5257	$166.53	$166.55	$166.50
Purchase #2	$58.63	12.169%	$65.7647	$65.76	$65.75	$65.80
Purchase #3	$180.95	3.762%	$187.7573	$187.76	$187.75	$187.80
Purchase #4	$183.76	9.212%	$200.688	$200.69	$200.70	$200.70
Purchase #5	$94.38	4.800%	$98.9102	$98.91	$98.90	$98.90
Purchase #6	$187.26	4.742%	$196.1399	$196.14	$196.15	$196.10
Purchase #7	$46.39	9.853%	$50.9608	$50.96	$50.95	$51.00
7 purchase totals =	$903.82		$966.7466	$966.75	$966.75	$966.80