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	$159.59	7.774%	$171.9965	$172.00	$172.00	$172.00
Purchase #2	$25.27	8.122%	$27.3224	$27.32	$27.30	$27.30
Purchase #3	$45.50	6.111%	$48.2805	$48.28	$48.30	$48.30
Purchase #4	$61.86	8.869%	$67.3464	$67.35	$67.35	$67.30
Purchase #5	$174.46	5.116%	$183.3854	$183.39	$183.40	$183.40
Purchase #6	$209.34	3.235%	$216.1121	$216.11	$216.10	$216.10
Purchase #7	$56.89	13.363%	$64.4922	$64.49	$64.50	$64.50
7 purchase totals =	$732.91		$778.9355	$778.94	$778.95	$778.90