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	$44.31	5.786%	$46.8738	$46.87	$46.85	$46.90
Purchase #2	$102.89	6.150%	$109.2177	$109.22	$109.20	$109.20
Purchase #3	$57.30	7.206%	$61.429	$61.43	$61.45	$61.40
Purchase #4	$64.99	11.135%	$72.2266	$72.23	$72.25	$72.20
Purchase #5	$248.42	11.808%	$277.7534	$277.75	$277.75	$277.80
Purchase #6	$130.59	7.521%	$140.4117	$140.41	$140.40	$140.40
Purchase #7	$18.71	13.780%	$21.2882	$21.29	$21.30	$21.30
7 purchase totals =	$667.21		$729.2004	$729.20	$729.20	$729.20