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	$143.81	10.674%	$159.1603	$159.16	$159.15	$159.20
Purchase #2	$85.69	11.335%	$95.403	$95.40	$95.40	$95.40
Purchase #3	$134.58	11.695%	$150.3191	$150.32	$150.30	$150.30
Purchase #4	$175.53	5.346%	$184.9138	$184.91	$184.90	$184.90
Purchase #5	$51.69	4.139%	$53.8294	$53.83	$53.85	$53.80
Purchase #6	$176.74	12.349%	$198.5656	$198.57	$198.55	$198.60
Purchase #7	$224.68	10.339%	$247.9097	$247.91	$247.90	$247.90
7 purchase totals =	$992.72		$1,090.1009	$1,090.10	$1,090.05	$1,090.10