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	$200.57	10.826%	$222.2837	$222.28	$222.30	$222.30
Purchase #2	$240.93	13.744%	$274.0434	$274.04	$274.05	$274.00
Purchase #3	$170.85	9.106%	$186.4076	$186.41	$186.40	$186.40
Purchase #4	$75.80	3.505%	$78.4568	$78.46	$78.45	$78.50
Purchase #5	$91.26	9.185%	$99.6422	$99.64	$99.65	$99.60
Purchase #6	$42.48	13.284%	$48.123	$48.12	$48.10	$48.10
Purchase #7	$90.54	6.112%	$96.0738	$96.07	$96.05	$96.10
7 purchase totals =	$912.43		$1,005.0305	$1,005.02	$1,005.00	$1,005.00