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	$151.36	3.667%	$156.9104	$156.91	$156.90	$156.90
Purchase #2	$85.78	4.648%	$89.7671	$89.77	$89.75	$89.80
Purchase #3	$28.98	11.816%	$32.4043	$32.40	$32.40	$32.40
Purchase #4	$167.44	3.399%	$173.1313	$173.13	$173.15	$173.10
Purchase #5	$53.33	3.539%	$55.2173	$55.22	$55.20	$55.20
Purchase #6	$59.78	10.625%	$66.1316	$66.13	$66.15	$66.10
Purchase #7	$172.30	12.147%	$193.2293	$193.23	$193.25	$193.20
7 purchase totals =	$718.97		$766.7913	$766.79	$766.80	$766.70