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	$187.36	4.830%	$196.4095	$196.41	$196.40	$196.40
Purchase #2	$110.31	4.194%	$114.9364	$114.94	$114.95	$114.90
Purchase #3	$93.59	9.407%	$102.394	$102.39	$102.40	$102.40
Purchase #4	$246.71	6.271%	$262.1812	$262.18	$262.20	$262.20
Purchase #5	$119.42	6.846%	$127.5955	$127.60	$127.60	$127.60
Purchase #6	$117.27	11.501%	$130.7572	$130.76	$130.75	$130.80
Purchase #7	$37.81	3.476%	$39.1243	$39.12	$39.10	$39.10
7 purchase totals =	$912.47		$973.3981	$973.40	$973.40	$973.40