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	$215.39	3.251%	$222.3923	$222.39	$222.40	$222.40
Purchase #2	$197.96	7.760%	$213.3217	$213.32	$213.30	$213.30
Purchase #3	$60.30	12.304%	$67.7193	$67.72	$67.70	$67.70
Purchase #4	$97.98	11.248%	$109.0008	$109.00	$109.00	$109.00
Purchase #5	$174.74	11.497%	$194.8299	$194.83	$194.85	$194.80
Purchase #6	$45.94	9.109%	$50.1247	$50.12	$50.10	$50.10
Purchase #7	$101.33	10.321%	$111.7883	$111.79	$111.80	$111.80
7 purchase totals =	$893.64		$969.1770	$969.17	$969.15	$969.10