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	$135.53	8.404%	$146.9199	$146.92	$146.90	$146.90
Purchase #2	$83.46	9.465%	$91.3595	$91.36	$91.35	$91.40
Purchase #3	$75.60	9.205%	$82.559	$82.56	$82.55	$82.60
Purchase #4	$195.96	13.497%	$222.4087	$222.41	$222.40	$222.40
Purchase #5	$107.95	9.599%	$118.3121	$118.31	$118.30	$118.30
Purchase #6	$190.41	9.376%	$208.2628	$208.26	$208.25	$208.30
Purchase #7	$43.89	6.644%	$46.8061	$46.81	$46.80	$46.80
7 purchase totals =	$832.80		$916.6281	$916.63	$916.55	$916.70