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	$173.61	10.555%	$191.9345	$191.93	$191.95	$191.90
Purchase #2	$116.60	10.288%	$128.5958	$128.60	$128.60	$128.60
Purchase #3	$144.64	5.308%	$152.3175	$152.32	$152.30	$152.30
Purchase #4	$159.44	13.735%	$181.3391	$181.34	$181.35	$181.30
Purchase #5	$90.69	7.646%	$97.6242	$97.62	$97.60	$97.60
Purchase #6	$91.36	13.526%	$103.7174	$103.72	$103.70	$103.70
Purchase #7	$25.61	8.793%	$27.8619	$27.86	$27.85	$27.90
7 purchase totals =	$801.95		$883.3904	$883.39	$883.35	$883.30