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	$35.82	3.735%	$37.1579	$37.16	$37.15	$37.20
Purchase #2	$91.32	7.422%	$98.0978	$98.10	$98.10	$98.10
Purchase #3	$118.56	5.334%	$124.884	$124.88	$124.90	$124.90
Purchase #4	$173.99	6.498%	$185.2959	$185.30	$185.30	$185.30
Purchase #5	$204.80	12.848%	$231.1127	$231.11	$231.10	$231.10
Purchase #6	$138.58	10.226%	$152.7512	$152.75	$152.75	$152.80
Purchase #7	$89.99	10.834%	$99.7395	$99.74	$99.75	$99.70
7 purchase totals =	$853.06		$929.0390	$929.04	$929.05	$929.10