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	$173.78	4.840%	$182.191	$182.19	$182.20	$182.20
Purchase #2	$34.64	8.500%	$37.5844	$37.58	$37.60	$37.60
Purchase #3	$57.93	7.269%	$62.1409	$62.14	$62.15	$62.10
Purchase #4	$213.56	8.538%	$231.7938	$231.79	$231.80	$231.80
Purchase #5	$201.69	10.296%	$222.456	$222.46	$222.45	$222.50
Purchase #6	$247.40	10.570%	$273.5502	$273.55	$273.55	$273.60
Purchase #7	$239.60	12.405%	$269.3224	$269.32	$269.30	$269.30
7 purchase totals =	$1,168.60		$1,279.0387	$1,279.03	$1,279.05	$1,279.10