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	$157.86	8.640%	$171.4991	$171.50	$171.50	$171.50
Purchase #2	$99.45	10.238%	$109.6317	$109.63	$109.65	$109.60
Purchase #3	$68.98	3.418%	$71.3377	$71.34	$71.35	$71.30
Purchase #4	$236.38	10.872%	$262.0792	$262.08	$262.10	$262.10
Purchase #5	$144.32	4.754%	$151.181	$151.18	$151.20	$151.20
Purchase #6	$217.69	12.546%	$245.0014	$245.00	$245.00	$245.00
Purchase #7	$175.88	4.370%	$183.566	$183.57	$183.55	$183.60
7 purchase totals =	$1,100.56		$1,194.2961	$1,194.30	$1,194.35	$1,194.30