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	$92.46	7.330%	$99.2373	$99.24	$99.25	$99.20
Purchase #2	$210.50	8.570%	$228.5399	$228.54	$228.55	$228.50
Purchase #3	$54.25	9.263%	$59.2752	$59.28	$59.30	$59.30
Purchase #4	$249.79	3.601%	$258.7849	$258.78	$258.80	$258.80
Purchase #5	$9.67	8.520%	$10.4939	$10.49	$10.50	$10.50
Purchase #6	$219.39	13.374%	$248.7312	$248.73	$248.75	$248.70
Purchase #7	$137.58	8.490%	$149.2605	$149.26	$149.25	$149.30
7 purchase totals =	$973.64		$1,054.3229	$1,054.32	$1,054.40	$1,054.30