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	$64.50	3.323%	$66.6433	$66.64	$66.65	$66.60
Purchase #2	$120.59	3.255%	$124.5152	$124.52	$124.50	$124.50
Purchase #3	$148.99	5.254%	$156.8179	$156.82	$156.80	$156.80
Purchase #4	$103.49	10.601%	$114.461	$114.46	$114.45	$114.50
Purchase #5	$89.52	7.443%	$96.183	$96.18	$96.20	$96.20
Purchase #6	$121.32	5.753%	$128.2995	$128.30	$128.30	$128.30
Purchase #7	$223.44	4.528%	$233.5574	$233.56	$233.55	$233.60
7 purchase totals =	$871.85		$920.4773	$920.48	$920.45	$920.50