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	$225.59	3.514%	$233.5172	$233.52	$233.50	$233.50
Purchase #2	$121.82	5.756%	$128.832	$128.83	$128.85	$128.80
Purchase #3	$70.97	7.674%	$76.4162	$76.42	$76.40	$76.40
Purchase #4	$142.83	5.297%	$150.3957	$150.40	$150.40	$150.40
Purchase #5	$131.39	3.303%	$135.7298	$135.73	$135.75	$135.70
Purchase #6	$30.97	4.331%	$32.3113	$32.31	$32.30	$32.30
Purchase #7	$246.32	11.751%	$275.2651	$275.27	$275.25	$275.30
7 purchase totals =	$969.89		$1,032.4673	$1,032.48	$1,032.45	$1,032.40