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	$22.62	9.276%	$24.7182	$24.72	$24.70	$24.70
Purchase #2	$33.58	11.219%	$37.3473	$37.35	$37.35	$37.30
Purchase #3	$109.79	9.219%	$119.9115	$119.91	$119.90	$119.90
Purchase #4	$151.70	3.203%	$156.559	$156.56	$156.55	$156.60
Purchase #5	$89.82	10.737%	$99.464	$99.46	$99.45	$99.50
Purchase #6	$181.33	11.677%	$202.5039	$202.50	$202.50	$202.50
Purchase #7	$72.64	11.421%	$80.9362	$80.94	$80.95	$80.90
7 purchase totals =	$661.48		$721.4401	$721.44	$721.40	$721.40