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	$198.56	5.346%	$209.175	$209.18	$209.20	$209.20
Purchase #2	$65.87	9.253%	$71.965	$71.97	$71.95	$72.00
Purchase #3	$213.79	7.461%	$229.7409	$229.74	$229.75	$229.70
Purchase #4	$230.28	8.330%	$249.4623	$249.46	$249.45	$249.50
Purchase #5	$152.86	11.130%	$169.8733	$169.87	$169.85	$169.90
Purchase #6	$85.57	4.472%	$89.3967	$89.40	$89.40	$89.40
Purchase #7	$115.70	13.149%	$130.9134	$130.91	$130.90	$130.90
7 purchase totals =	$1,062.63		$1,150.5266	$1,150.53	$1,150.50	$1,150.60