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	$196.97	11.574%	$219.7673	$219.77	$219.75	$219.80
Purchase #2	$225.59	3.333%	$233.1089	$233.11	$233.10	$233.10
Purchase #3	$49.71	8.131%	$53.7519	$53.75	$53.75	$53.80
Purchase #4	$113.43	4.490%	$118.523	$118.52	$118.50	$118.50
Purchase #5	$171.98	9.646%	$188.5692	$188.57	$188.55	$188.60
Purchase #6	$22.97	12.163%	$25.7638	$25.76	$25.75	$25.80
Purchase #7	$78.88	13.498%	$89.5272	$89.53	$89.55	$89.50
7 purchase totals =	$859.53		$929.0113	$929.01	$928.95	$929.10