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	$145.79	11.578%	$162.6696	$162.67	$162.65	$162.70
Purchase #2	$67.91	8.701%	$73.8188	$73.82	$73.80	$73.80
Purchase #3	$168.85	11.723%	$188.6443	$188.64	$188.65	$188.60
Purchase #4	$82.42	8.460%	$89.3927	$89.39	$89.40	$89.40
Purchase #5	$109.32	10.530%	$120.8314	$120.83	$120.85	$120.80
Purchase #6	$107.40	7.371%	$115.3165	$115.32	$115.30	$115.30
Purchase #7	$193.83	3.608%	$200.8234	$200.82	$200.80	$200.80
7 purchase totals =	$875.52		$951.4967	$951.49	$951.45	$951.40