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	$174.36	8.196%	$188.6505	$188.65	$188.65	$188.70
Purchase #2	$86.45	3.438%	$89.4222	$89.42	$89.40	$89.40
Purchase #3	$93.61	8.815%	$101.8617	$101.86	$101.85	$101.90
Purchase #4	$139.92	9.127%	$152.6905	$152.69	$152.70	$152.70
Purchase #5	$9.33	10.349%	$10.2956	$10.30	$10.30	$10.30
Purchase #6	$227.27	12.862%	$256.5015	$256.50	$256.50	$256.50
Purchase #7	$203.72	8.483%	$221.0016	$221.00	$221.00	$221.00
7 purchase totals =	$934.66		$1,020.4236	$1,020.42	$1,020.40	$1,020.50