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	$153.62	6.755%	$163.997	$164.00	$164.00	$164.00
Purchase #2	$181.62	10.412%	$200.5303	$200.53	$200.55	$200.50
Purchase #3	$99.77	9.808%	$109.5554	$109.56	$109.55	$109.60
Purchase #4	$91.83	6.556%	$97.8504	$97.85	$97.85	$97.90
Purchase #5	$46.58	13.190%	$52.7239	$52.72	$52.70	$52.70
Purchase #6	$69.97	11.736%	$78.1817	$78.18	$78.20	$78.20
Purchase #7	$27.53	13.743%	$31.3134	$31.31	$31.30	$31.30
7 purchase totals =	$670.92		$734.1521	$734.15	$734.15	$734.20