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	$211.90	8.431%	$229.7653	$229.77	$229.75	$229.80
Purchase #2	$41.99	12.640%	$47.2975	$47.30	$47.30	$47.30
Purchase #3	$176.89	12.418%	$198.8562	$198.86	$198.85	$198.90
Purchase #4	$6.52	11.521%	$7.2712	$7.27	$7.25	$7.30
Purchase #5	$176.51	6.429%	$187.8578	$187.86	$187.85	$187.90
Purchase #6	$196.56	13.417%	$222.9325	$222.93	$222.95	$222.90
Purchase #7	$213.28	3.107%	$219.9066	$219.91	$219.90	$219.90
7 purchase totals =	$1,023.65		$1,113.8871	$1,113.90	$1,113.85	$1,114.00