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	$115.95	6.215%	$123.1563	$123.16	$123.15	$123.20
Purchase #2	$12.42	10.752%	$13.7554	$13.76	$13.75	$13.80
Purchase #3	$228.86	6.530%	$243.8046	$243.80	$243.80	$243.80
Purchase #4	$29.33	10.207%	$32.3237	$32.32	$32.30	$32.30
Purchase #5	$25.91	5.487%	$27.3317	$27.33	$27.35	$27.30
Purchase #6	$226.69	12.794%	$255.6927	$255.69	$255.70	$255.70
Purchase #7	$179.98	4.533%	$188.1385	$188.14	$188.15	$188.10
7 purchase totals =	$819.14		$884.2029	$884.20	$884.20	$884.20