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	$140.63	9.741%	$154.3288	$154.33	$154.35	$154.30
Purchase #2	$225.85	6.396%	$240.2954	$240.30	$240.30	$240.30
Purchase #3	$242.48	13.609%	$275.4791	$275.48	$275.50	$275.50
Purchase #4	$160.50	11.728%	$179.3234	$179.32	$179.30	$179.30
Purchase #5	$88.28	11.733%	$98.6379	$98.64	$98.65	$98.60
Purchase #6	$86.94	10.458%	$96.0322	$96.03	$96.05	$96.00
Purchase #7	$120.37	5.610%	$127.1228	$127.12	$127.10	$127.10
7 purchase totals =	$1,065.05		$1,171.2196	$1,171.22	$1,171.25	$1,171.10