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	$96.56	8.363%	$104.6353	$104.64	$104.65	$104.60
Purchase #2	$167.74	11.108%	$186.3726	$186.37	$186.35	$186.40
Purchase #3	$102.85	8.628%	$111.7239	$111.72	$111.70	$111.70
Purchase #4	$119.61	9.866%	$131.4107	$131.41	$131.40	$131.40
Purchase #5	$137.36	6.813%	$146.7183	$146.72	$146.70	$146.70
Purchase #6	$135.35	12.606%	$152.4122	$152.41	$152.40	$152.40
Purchase #7	$214.79	13.336%	$243.4344	$243.43	$243.45	$243.40
7 purchase totals =	$974.26		$1,076.7074	$1,076.70	$1,076.65	$1,076.60