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	$196.40	7.240%	$210.6194	$210.62	$210.60	$210.60
Purchase #2	$142.63	5.644%	$150.68	$150.68	$150.70	$150.70
Purchase #3	$59.85	9.356%	$65.4496	$65.45	$65.45	$65.40
Purchase #4	$227.41	7.673%	$244.8592	$244.86	$244.85	$244.90
Purchase #5	$42.89	11.715%	$47.9146	$47.91	$47.90	$47.90
Purchase #6	$176.27	8.256%	$190.8229	$190.82	$190.80	$190.80
Purchase #7	$94.76	12.390%	$106.5008	$106.50	$106.50	$106.50
7 purchase totals =	$940.21		$1,016.8465	$1,016.84	$1,016.80	$1,016.80