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	$10.31	13.715%	$11.724	$11.72	$11.70	$11.70
Purchase #2	$226.63	13.199%	$256.5429	$256.54	$256.55	$256.50
Purchase #3	$223.51	7.856%	$241.0689	$241.07	$241.05	$241.10
Purchase #4	$175.63	6.221%	$186.5559	$186.56	$186.55	$186.60
Purchase #5	$67.79	13.669%	$77.0562	$77.06	$77.05	$77.10
Purchase #6	$248.85	6.114%	$264.0647	$264.06	$264.05	$264.10
Purchase #7	$42.84	3.372%	$44.2846	$44.28	$44.30	$44.30
7 purchase totals =	$995.56		$1,081.2972	$1,081.29	$1,081.25	$1,081.40