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	$50.42	3.342%	$52.105	$52.11	$52.10	$52.10
Purchase #2	$124.72	10.787%	$138.1735	$138.17	$138.15	$138.20
Purchase #3	$196.33	7.833%	$211.7085	$211.71	$211.70	$211.70
Purchase #4	$114.75	10.831%	$127.1786	$127.18	$127.20	$127.20
Purchase #5	$210.92	12.422%	$237.1205	$237.12	$237.10	$237.10
Purchase #6	$201.69	10.258%	$222.3794	$222.38	$222.40	$222.40
Purchase #7	$108.34	3.845%	$112.5057	$112.51	$112.50	$112.50
7 purchase totals =	$1,007.17		$1,101.1712	$1,101.18	$1,101.15	$1,101.20