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	$98.70	10.613%	$109.175	$109.18	$109.20	$109.20
Purchase #2	$47.81	4.649%	$50.0327	$50.03	$50.05	$50.00
Purchase #3	$159.56	3.417%	$165.0122	$165.01	$165.00	$165.00
Purchase #4	$179.90	11.536%	$200.6533	$200.65	$200.65	$200.70
Purchase #5	$204.72	12.154%	$229.6017	$229.60	$229.60	$229.60
Purchase #6	$88.36	4.420%	$92.2655	$92.27	$92.25	$92.30
Purchase #7	$221.66	10.449%	$244.8213	$244.82	$244.80	$244.80
7 purchase totals =	$1,000.71		$1,091.5617	$1,091.56	$1,091.55	$1,091.60