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	$198.87	6.128%	$211.0568	$211.06	$211.05	$211.10
Purchase #2	$144.73	3.862%	$150.3195	$150.32	$150.30	$150.30
Purchase #3	$89.82	3.428%	$92.899	$92.90	$92.90	$92.90
Purchase #4	$142.51	5.867%	$150.8711	$150.87	$150.85	$150.90
Purchase #5	$225.45	10.367%	$248.8224	$248.82	$248.80	$248.80
Purchase #6	$135.60	5.197%	$142.6471	$142.65	$142.65	$142.60
Purchase #7	$120.79	8.243%	$130.7467	$130.75	$130.75	$130.70
7 purchase totals =	$1,057.77		$1,127.3626	$1,127.37	$1,127.30	$1,127.30