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	$44.79	4.676%	$46.8844	$46.88	$46.90	$46.90
Purchase #2	$187.95	4.755%	$196.887	$196.89	$196.90	$196.90
Purchase #3	$96.95	4.598%	$101.4078	$101.41	$101.40	$101.40
Purchase #4	$105.51	9.597%	$115.6358	$115.64	$115.65	$115.60
Purchase #5	$162.53	4.149%	$169.2734	$169.27	$169.25	$169.30
Purchase #6	$48.46	11.569%	$54.0663	$54.07	$54.05	$54.10
Purchase #7	$95.33	3.171%	$98.3529	$98.35	$98.35	$98.40
7 purchase totals =	$741.52		$782.5076	$782.51	$782.50	$782.60