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	$204.61	7.477%	$219.9087	$219.91	$219.90	$219.90
Purchase #2	$75.94	3.218%	$78.3837	$78.38	$78.40	$78.40
Purchase #3	$195.82	9.129%	$213.6964	$213.70	$213.70	$213.70
Purchase #4	$193.56	9.264%	$211.4914	$211.49	$211.50	$211.50
Purchase #5	$79.46	4.247%	$82.8347	$82.83	$82.85	$82.80
Purchase #6	$26.53	7.737%	$28.5826	$28.58	$28.60	$28.60
Purchase #7	$104.91	6.199%	$111.4134	$111.41	$111.40	$111.40
7 purchase totals =	$880.83		$946.3109	$946.30	$946.35	$946.30