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	$47.82	12.613%	$53.8515	$53.85	$53.85	$53.90
Purchase #2	$79.47	5.431%	$83.786	$83.79	$83.80	$83.80
Purchase #3	$160.37	13.614%	$182.2028	$182.20	$182.20	$182.20
Purchase #4	$104.88	4.714%	$109.824	$109.82	$109.80	$109.80
Purchase #5	$36.65	7.123%	$39.2606	$39.26	$39.25	$39.30
Purchase #6	$81.80	12.238%	$91.8107	$91.81	$91.80	$91.80
Purchase #7	$88.27	11.806%	$98.6912	$98.69	$98.70	$98.70
7 purchase totals =	$599.26		$659.4268	$659.42	$659.40	$659.50