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	$170.88	13.248%	$193.5182	$193.52	$193.50	$193.50
Purchase #2	$85.26	13.319%	$96.6158	$96.62	$96.60	$96.60
Purchase #3	$121.44	5.260%	$127.8277	$127.83	$127.85	$127.80
Purchase #4	$142.65	11.821%	$159.5127	$159.51	$159.50	$159.50
Purchase #5	$78.26	10.807%	$86.7176	$86.72	$86.70	$86.70
Purchase #6	$205.81	7.644%	$221.5421	$221.54	$221.55	$221.50
Purchase #7	$131.69	6.754%	$140.5843	$140.58	$140.60	$140.60
7 purchase totals =	$935.99		$1,026.3184	$1,026.32	$1,026.30	$1,026.20