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	$169.38	13.133%	$191.6247	$191.62	$191.60	$191.60
Purchase #2	$199.25	4.756%	$208.7263	$208.73	$208.75	$208.70
Purchase #3	$149.74	8.543%	$162.5323	$162.53	$162.55	$162.50
Purchase #4	$56.37	11.342%	$62.7635	$62.76	$62.75	$62.80
Purchase #5	$136.80	11.376%	$152.3624	$152.36	$152.35	$152.40
Purchase #6	$145.28	3.809%	$150.8137	$150.81	$150.80	$150.80
Purchase #7	$126.94	7.446%	$136.392	$136.39	$136.40	$136.40
7 purchase totals =	$983.76		$1,065.2149	$1,065.20	$1,065.20	$1,065.20