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	$135.52	6.630%	$144.505	$144.51	$144.50	$144.50
Purchase #2	$114.66	10.259%	$126.423	$126.42	$126.40	$126.40
Purchase #3	$142.69	12.459%	$160.4677	$160.47	$160.45	$160.50
Purchase #4	$69.37	12.707%	$78.1848	$78.18	$78.20	$78.20
Purchase #5	$247.32	7.124%	$264.9391	$264.94	$264.95	$264.90
Purchase #6	$84.55	4.395%	$88.266	$88.27	$88.25	$88.30
Purchase #7	$211.73	5.267%	$222.8818	$222.88	$222.90	$222.90
7 purchase totals =	$1,005.84		$1,085.6674	$1,085.67	$1,085.65	$1,085.70