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	$215.44	6.633%	$229.7301	$229.73	$229.75	$229.70
Purchase #2	$89.48	10.546%	$98.9166	$98.92	$98.90	$98.90
Purchase #3	$57.71	13.538%	$65.5228	$65.52	$65.50	$65.50
Purchase #4	$189.32	10.798%	$209.7628	$209.76	$209.75	$209.80
Purchase #5	$244.59	7.532%	$263.0125	$263.01	$263.00	$263.00
Purchase #6	$22.65	13.842%	$25.7852	$25.79	$25.80	$25.80
Purchase #7	$57.70	3.816%	$59.9018	$59.90	$59.90	$59.90
7 purchase totals =	$876.89		$952.6318	$952.63	$952.60	$952.60