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	$107.65	3.534%	$111.4544	$111.45	$111.45	$111.50
Purchase #2	$101.99	4.826%	$106.912	$106.91	$106.90	$106.90
Purchase #3	$27.35	13.744%	$31.109	$31.11	$31.10	$31.10
Purchase #4	$55.33	8.294%	$59.9191	$59.92	$59.90	$59.90
Purchase #5	$55.50	12.386%	$62.3742	$62.37	$62.35	$62.40
Purchase #6	$125.87	4.309%	$131.2937	$131.29	$131.30	$131.30
Purchase #7	$121.45	5.483%	$128.1091	$128.11	$128.10	$128.10
7 purchase totals =	$595.14		$631.1715	$631.16	$631.10	$631.20