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	$91.62	12.295%	$102.8847	$102.88	$102.90	$102.90
Purchase #2	$69.26	4.151%	$72.135	$72.14	$72.15	$72.10
Purchase #3	$148.54	4.534%	$155.2748	$155.27	$155.25	$155.30
Purchase #4	$223.92	12.154%	$251.1352	$251.14	$251.15	$251.10
Purchase #5	$139.84	11.730%	$156.2432	$156.24	$156.25	$156.20
Purchase #6	$245.42	4.241%	$255.8283	$255.83	$255.85	$255.80
Purchase #7	$47.55	10.594%	$52.5874	$52.59	$52.60	$52.60
7 purchase totals =	$966.15		$1,046.0886	$1,046.09	$1,046.15	$1,046.00