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	$102.73	4.443%	$107.2943	$107.29	$107.30	$107.30
Purchase #2	$151.75	8.472%	$164.6063	$164.61	$164.60	$164.60
Purchase #3	$146.83	13.237%	$166.2659	$166.27	$166.25	$166.30
Purchase #4	$148.48	5.448%	$156.5692	$156.57	$156.55	$156.60
Purchase #5	$59.53	3.527%	$61.6296	$61.63	$61.65	$61.60
Purchase #6	$218.60	11.250%	$243.1925	$243.19	$243.20	$243.20
Purchase #7	$216.34	12.350%	$243.058	$243.06	$243.05	$243.10
7 purchase totals =	$1,044.26		$1,142.6158	$1,142.62	$1,142.60	$1,142.70