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	$90.51	13.526%	$102.7524	$102.75	$102.75	$102.80
Purchase #2	$93.64	9.504%	$102.5395	$102.54	$102.55	$102.50
Purchase #3	$230.47	6.191%	$244.7384	$244.74	$244.75	$244.70
Purchase #4	$242.56	12.411%	$272.6641	$272.66	$272.65	$272.70
Purchase #5	$92.92	9.243%	$101.5086	$101.51	$101.50	$101.50
Purchase #6	$98.40	6.274%	$104.5736	$104.57	$104.55	$104.60
Purchase #7	$116.61	12.806%	$131.5431	$131.54	$131.55	$131.50
7 purchase totals =	$965.11		$1,060.3197	$1,060.31	$1,060.30	$1,060.30