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	$77.69	11.525%	$86.6438	$86.64	$86.65	$86.60
Purchase #2	$58.30	8.546%	$63.2823	$63.28	$63.30	$63.30
Purchase #3	$161.35	13.366%	$182.916	$182.92	$182.90	$182.90
Purchase #4	$56.25	5.646%	$59.4259	$59.43	$59.45	$59.40
Purchase #5	$100.72	5.616%	$106.3764	$106.38	$106.40	$106.40
Purchase #6	$194.91	11.289%	$216.9134	$216.91	$216.90	$216.90
Purchase #7	$195.72	5.450%	$206.3867	$206.39	$206.40	$206.40
7 purchase totals =	$844.94		$921.9445	$921.95	$922.00	$921.90