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	$98.36	13.677%	$111.8127	$111.81	$111.80	$111.80
Purchase #2	$7.31	6.112%	$7.7568	$7.76	$7.75	$7.80
Purchase #3	$128.80	11.354%	$143.424	$143.42	$143.40	$143.40
Purchase #4	$85.62	4.498%	$89.4712	$89.47	$89.45	$89.50
Purchase #5	$133.77	13.701%	$152.0978	$152.10	$152.10	$152.10
Purchase #6	$184.95	10.505%	$204.379	$204.38	$204.40	$204.40
Purchase #7	$192.57	11.688%	$215.0776	$215.08	$215.10	$215.10
7 purchase totals =	$831.38		$924.0191	$924.02	$924.00	$924.10