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	$174.59	13.183%	$197.6062	$197.61	$197.60	$197.60
Purchase #2	$62.88	7.293%	$67.4658	$67.47	$67.45	$67.50
Purchase #3	$82.50	6.293%	$87.6917	$87.69	$87.70	$87.70
Purchase #4	$216.97	11.666%	$242.2817	$242.28	$242.30	$242.30
Purchase #5	$231.57	6.737%	$247.1709	$247.17	$247.15	$247.20
Purchase #6	$199.98	11.369%	$222.7157	$222.72	$222.70	$222.70
Purchase #7	$77.33	3.816%	$80.2809	$80.28	$80.30	$80.30
7 purchase totals =	$1,045.82		$1,145.2129	$1,145.22	$1,145.20	$1,145.30