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	$186.46	7.761%	$200.9312	$200.93	$200.95	$200.90
Purchase #2	$89.62	11.747%	$100.1477	$100.15	$100.15	$100.10
Purchase #3	$237.77	9.463%	$260.2702	$260.27	$260.25	$260.30
Purchase #4	$206.97	11.808%	$231.409	$231.41	$231.40	$231.40
Purchase #5	$41.88	6.297%	$44.5172	$44.52	$44.50	$44.50
Purchase #6	$56.46	3.769%	$58.588	$58.59	$58.60	$58.60
Purchase #7	$21.44	4.700%	$22.4477	$22.45	$22.45	$22.40
7 purchase totals =	$840.60		$918.3110	$918.32	$918.30	$918.20