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	$30.79	13.616%	$34.9824	$34.98	$35.00	$35.00
Purchase #2	$60.54	11.192%	$67.3156	$67.32	$67.30	$67.30
Purchase #3	$67.40	10.128%	$74.2263	$74.23	$74.25	$74.20
Purchase #4	$79.78	12.501%	$89.7533	$89.75	$89.75	$89.80
Purchase #5	$140.85	10.829%	$156.1026	$156.10	$156.10	$156.10
Purchase #6	$221.75	10.689%	$245.4529	$245.45	$245.45	$245.50
Purchase #7	$88.57	4.445%	$92.5069	$92.51	$92.50	$92.50
7 purchase totals =	$689.68		$760.3400	$760.34	$760.35	$760.40