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	$73.69	11.342%	$82.0479	$82.05	$82.05	$82.00
Purchase #2	$48.91	13.610%	$55.5667	$55.57	$55.55	$55.60
Purchase #3	$54.44	11.116%	$60.4916	$60.49	$60.50	$60.50
Purchase #4	$227.47	12.399%	$255.674	$255.67	$255.65	$255.70
Purchase #5	$94.25	3.765%	$97.7985	$97.80	$97.80	$97.80
Purchase #6	$145.27	7.442%	$156.081	$156.08	$156.10	$156.10
Purchase #7	$42.72	6.682%	$45.5746	$45.57	$45.55	$45.60
7 purchase totals =	$686.75		$753.2343	$753.23	$753.20	$753.30