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	$221.41	7.250%	$237.4622	$237.46	$237.45	$237.50
Purchase #2	$174.89	3.155%	$180.4078	$180.41	$180.40	$180.40
Purchase #3	$151.46	10.842%	$167.8813	$167.88	$167.90	$167.90
Purchase #4	$227.92	6.755%	$243.316	$243.32	$243.30	$243.30
Purchase #5	$231.27	13.143%	$261.6658	$261.67	$261.65	$261.70
Purchase #6	$166.79	4.276%	$173.9219	$173.92	$173.90	$173.90
Purchase #7	$45.74	8.264%	$49.52	$49.52	$49.50	$49.50
7 purchase totals =	$1,219.48		$1,314.1750	$1,314.18	$1,314.10	$1,314.20