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	$144.61	3.404%	$149.5325	$149.53	$149.55	$149.50
Purchase #2	$142.83	7.803%	$153.975	$153.98	$154.00	$154.00
Purchase #3	$148.43	5.204%	$156.1543	$156.15	$156.15	$156.20
Purchase #4	$104.45	10.691%	$115.6167	$115.62	$115.60	$115.60
Purchase #5	$166.52	3.479%	$172.3132	$172.31	$172.30	$172.30
Purchase #6	$219.63	6.486%	$233.8752	$233.88	$233.90	$233.90
Purchase #7	$85.67	5.502%	$90.3836	$90.38	$90.40	$90.40
7 purchase totals =	$1,012.14		$1,071.8505	$1,071.85	$1,071.90	$1,071.90