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	$217.25	6.218%	$230.7586	$230.76	$230.75	$230.80
Purchase #2	$31.71	11.319%	$35.2993	$35.30	$35.30	$35.30
Purchase #3	$248.32	6.137%	$263.5594	$263.56	$263.55	$263.60
Purchase #4	$136.56	11.752%	$152.6085	$152.61	$152.60	$152.60
Purchase #5	$120.91	8.717%	$131.4497	$131.45	$131.45	$131.40
Purchase #6	$44.44	4.130%	$46.2754	$46.28	$46.30	$46.30
Purchase #7	$151.52	11.839%	$169.4585	$169.46	$169.45	$169.50
7 purchase totals =	$950.71		$1,029.4094	$1,029.42	$1,029.40	$1,029.50