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	$142.55	13.289%	$161.4935	$161.49	$161.50	$161.50
Purchase #2	$112.64	6.716%	$120.2049	$120.20	$120.20	$120.20
Purchase #3	$174.87	13.528%	$198.5264	$198.53	$198.55	$198.50
Purchase #4	$147.89	12.592%	$166.5123	$166.51	$166.50	$166.50
Purchase #5	$40.61	7.253%	$43.5554	$43.56	$43.55	$43.60
Purchase #6	$244.56	7.728%	$263.4596	$263.46	$263.45	$263.50
Purchase #7	$240.82	4.449%	$251.5341	$251.53	$251.55	$251.50
7 purchase totals =	$1,103.94		$1,205.2862	$1,205.28	$1,205.30	$1,205.30