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	$174.88	7.765%	$188.4594	$188.46	$188.45	$188.50
Purchase #2	$201.64	10.279%	$222.3666	$222.37	$222.35	$222.40
Purchase #3	$53.95	10.483%	$59.6056	$59.61	$59.60	$59.60
Purchase #4	$142.68	6.659%	$152.1811	$152.18	$152.20	$152.20
Purchase #5	$103.32	12.398%	$116.1296	$116.13	$116.15	$116.10
Purchase #6	$204.99	8.562%	$222.5412	$222.54	$222.55	$222.50
Purchase #7	$176.33	11.547%	$196.6908	$196.69	$196.70	$196.70
7 purchase totals =	$1,057.79		$1,157.9743	$1,157.98	$1,158.00	$1,158.00