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	$94.33	10.114%	$103.8705	$103.87	$103.85	$103.90
Purchase #2	$89.87	13.350%	$101.8676	$101.87	$101.85	$101.90
Purchase #3	$206.96	10.817%	$229.3469	$229.35	$229.35	$229.30
Purchase #4	$182.60	11.869%	$204.2728	$204.27	$204.25	$204.30
Purchase #5	$90.41	13.434%	$102.5557	$102.56	$102.55	$102.60
Purchase #6	$76.93	11.231%	$85.57	$85.57	$85.55	$85.60
Purchase #7	$216.40	13.381%	$245.3565	$245.36	$245.35	$245.40
7 purchase totals =	$957.50		$1,072.8400	$1,072.85	$1,072.75	$1,073.00