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	$186.77	13.570%	$212.1147	$212.11	$212.10	$212.10
Purchase #2	$79.44	7.786%	$85.6252	$85.63	$85.65	$85.60
Purchase #3	$160.38	4.326%	$167.318	$167.32	$167.30	$167.30
Purchase #4	$171.44	9.750%	$188.1554	$188.16	$188.15	$188.20
Purchase #5	$132.55	4.765%	$138.866	$138.87	$138.85	$138.90
Purchase #6	$72.43	13.361%	$82.1074	$82.11	$82.10	$82.10
Purchase #7	$200.81	10.241%	$221.375	$221.38	$221.40	$221.40
7 purchase totals =	$1,003.82		$1,095.5617	$1,095.58	$1,095.55	$1,095.60