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	$183.46	4.279%	$191.3103	$191.31	$191.30	$191.30
Purchase #2	$164.28	5.128%	$172.7043	$172.70	$172.70	$172.70
Purchase #3	$83.64	6.545%	$89.1142	$89.11	$89.10	$89.10
Purchase #4	$69.43	4.439%	$72.512	$72.51	$72.50	$72.50
Purchase #5	$89.51	8.261%	$96.9044	$96.90	$96.90	$96.90
Purchase #6	$103.66	11.338%	$115.413	$115.41	$115.40	$115.40
Purchase #7	$228.59	12.612%	$257.4198	$257.42	$257.40	$257.40
7 purchase totals =	$922.57		$995.3780	$995.36	$995.30	$995.30