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	$67.91	4.207%	$70.767	$70.77	$70.75	$70.80
Purchase #2	$39.88	7.521%	$42.8794	$42.88	$42.90	$42.90
Purchase #3	$39.75	7.425%	$42.7014	$42.70	$42.70	$42.70
Purchase #4	$73.82	11.292%	$82.1558	$82.16	$82.15	$82.20
Purchase #5	$91.94	13.603%	$104.4466	$104.45	$104.45	$104.40
Purchase #6	$199.50	13.441%	$226.3148	$226.31	$226.30	$226.30
Purchase #7	$132.79	9.437%	$145.3214	$145.32	$145.30	$145.30
7 purchase totals =	$645.59		$714.5864	$714.59	$714.55	$714.60