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	$84.78	13.862%	$96.5322	$96.53	$96.55	$96.50
Purchase #2	$41.46	5.811%	$43.8692	$43.87	$43.85	$43.90
Purchase #3	$49.43	4.583%	$51.6954	$51.70	$51.70	$51.70
Purchase #4	$108.73	6.596%	$115.9018	$115.90	$115.90	$115.90
Purchase #5	$70.93	9.813%	$77.8904	$77.89	$77.90	$77.90
Purchase #6	$169.42	9.377%	$185.3065	$185.31	$185.30	$185.30
Purchase #7	$28.38	6.779%	$30.3039	$30.30	$30.30	$30.30
7 purchase totals =	$553.13		$601.4994	$601.50	$601.50	$601.50