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	$193.47	5.168%	$203.4685	$203.47	$203.45	$203.50
Purchase #2	$172.76	8.249%	$187.011	$187.01	$187.00	$187.00
Purchase #3	$172.39	4.738%	$180.5578	$180.56	$180.55	$180.60
Purchase #4	$91.64	9.543%	$100.3852	$100.39	$100.40	$100.40
Purchase #5	$67.73	8.597%	$73.5527	$73.55	$73.55	$73.60
Purchase #6	$211.81	10.419%	$233.8785	$233.88	$233.90	$233.90
Purchase #7	$166.91	10.110%	$183.7846	$183.78	$183.80	$183.80
7 purchase totals =	$1,076.71		$1,162.6383	$1,162.64	$1,162.65	$1,162.80