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	$89.48	10.243%	$98.6454	$98.65	$98.65	$98.60
Purchase #2	$151.70	6.409%	$161.4225	$161.42	$161.40	$161.40
Purchase #3	$92.40	13.687%	$105.0468	$105.05	$105.05	$105.00
Purchase #4	$174.54	3.776%	$181.1306	$181.13	$181.15	$181.10
Purchase #5	$68.97	4.217%	$71.8785	$71.88	$71.90	$71.90
Purchase #6	$154.56	8.802%	$168.1644	$168.16	$168.15	$168.20
Purchase #7	$45.25	6.236%	$48.0718	$48.07	$48.05	$48.10
7 purchase totals =	$776.90		$834.3600	$834.36	$834.35	$834.30