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	$129.61	10.112%	$142.7162	$142.72	$142.70	$142.70
Purchase #2	$192.88	12.424%	$216.8434	$216.84	$216.85	$216.80
Purchase #3	$84.56	13.520%	$95.9925	$95.99	$96.00	$96.00
Purchase #4	$74.79	10.171%	$82.3969	$82.40	$82.40	$82.40
Purchase #5	$167.92	7.492%	$180.5006	$180.50	$180.50	$180.50
Purchase #6	$123.91	5.592%	$130.839	$130.84	$130.85	$130.80
Purchase #7	$98.67	12.507%	$111.0107	$111.01	$111.00	$111.00
7 purchase totals =	$872.34		$960.2993	$960.30	$960.30	$960.20