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	$128.97	10.347%	$142.3145	$142.31	$142.30	$142.30
Purchase #2	$103.54	4.678%	$108.3836	$108.38	$108.40	$108.40
Purchase #3	$38.74	9.290%	$42.3389	$42.34	$42.35	$42.30
Purchase #4	$121.55	5.284%	$127.9727	$127.97	$127.95	$128.00
Purchase #5	$114.35	11.740%	$127.7747	$127.77	$127.75	$127.80
Purchase #6	$11.36	8.119%	$12.2823	$12.28	$12.30	$12.30
Purchase #7	$14.46	3.231%	$14.9272	$14.93	$14.95	$14.90
7 purchase totals =	$532.97		$575.9939	$575.98	$576.00	$576.00