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	$53.42	4.586%	$55.8698	$55.87	$55.85	$55.90
Purchase #2	$85.89	5.673%	$90.7625	$90.76	$90.75	$90.80
Purchase #3	$98.43	4.717%	$103.0729	$103.07	$103.05	$103.10
Purchase #4	$10.26	7.647%	$11.0446	$11.04	$11.05	$11.00
Purchase #5	$235.60	4.399%	$245.964	$245.96	$245.95	$246.00
Purchase #6	$186.54	5.592%	$196.9713	$196.97	$196.95	$197.00
Purchase #7	$222.42	6.682%	$237.2821	$237.28	$237.30	$237.30
7 purchase totals =	$892.56		$940.9672	$940.95	$940.90	$941.10