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	$172.92	8.300%	$187.2724	$187.27	$187.25	$187.30
Purchase #2	$191.75	12.843%	$216.3765	$216.38	$216.40	$216.40
Purchase #3	$97.91	13.778%	$111.4	$111.40	$111.40	$111.40
Purchase #4	$220.39	13.798%	$250.7994	$250.80	$250.80	$250.80
Purchase #5	$35.91	4.117%	$37.3884	$37.39	$37.40	$37.40
Purchase #6	$114.71	13.630%	$130.345	$130.35	$130.35	$130.30
Purchase #7	$197.27	11.183%	$219.3307	$219.33	$219.35	$219.30
7 purchase totals =	$1,030.86		$1,152.9124	$1,152.92	$1,152.95	$1,152.90