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	$100.26	11.296%	$111.5854	$111.59	$111.60	$111.60
Purchase #2	$198.75	4.818%	$208.3258	$208.33	$208.35	$208.30
Purchase #3	$55.80	6.705%	$59.5414	$59.54	$59.55	$59.50
Purchase #4	$233.26	11.865%	$260.9363	$260.94	$260.95	$260.90
Purchase #5	$133.25	13.112%	$150.7217	$150.72	$150.70	$150.70
Purchase #6	$216.28	3.415%	$223.666	$223.67	$223.65	$223.70
Purchase #7	$211.94	8.333%	$229.601	$229.60	$229.60	$229.60
7 purchase totals =	$1,149.54		$1,244.3776	$1,244.39	$1,244.40	$1,244.30