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	$99.93	4.482%	$104.4089	$104.41	$104.40	$104.40
Purchase #2	$65.85	11.332%	$73.3121	$73.31	$73.30	$73.30
Purchase #3	$83.37	8.485%	$90.4439	$90.44	$90.45	$90.40
Purchase #4	$177.27	12.679%	$199.7461	$199.75	$199.75	$199.70
Purchase #5	$164.90	4.473%	$172.276	$172.28	$172.30	$172.30
Purchase #6	$133.26	13.159%	$150.7957	$150.80	$150.80	$150.80
Purchase #7	$217.90	5.515%	$229.9172	$229.92	$229.90	$229.90
7 purchase totals =	$942.48		$1,020.8999	$1,020.91	$1,020.90	$1,020.80