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	$106.93	8.792%	$116.3313	$116.33	$116.35	$116.30
Purchase #2	$147.30	10.169%	$162.2789	$162.28	$162.30	$162.30
Purchase #3	$52.41	12.178%	$58.7925	$58.79	$58.80	$58.80
Purchase #4	$94.50	9.521%	$103.4973	$103.50	$103.50	$103.50
Purchase #5	$43.94	5.688%	$46.4393	$46.44	$46.45	$46.40
Purchase #6	$80.28	11.320%	$89.3677	$89.37	$89.35	$89.40
Purchase #7	$171.75	4.682%	$179.7913	$179.79	$179.80	$179.80
7 purchase totals =	$697.11		$756.4983	$756.50	$756.55	$756.50