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	$181.57	8.465%	$196.9399	$196.94	$196.95	$196.90
Purchase #2	$247.45	6.773%	$264.2098	$264.21	$264.20	$264.20
Purchase #3	$247.72	4.871%	$259.7864	$259.79	$259.80	$259.80
Purchase #4	$99.54	5.818%	$105.3312	$105.33	$105.35	$105.30
Purchase #5	$205.77	12.550%	$231.5941	$231.59	$231.60	$231.60
Purchase #6	$26.26	4.618%	$27.4727	$27.47	$27.45	$27.50
Purchase #7	$139.59	4.597%	$146.007	$146.01	$146.00	$146.00
7 purchase totals =	$1,147.90		$1,231.3411	$1,231.34	$1,231.35	$1,231.30