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	$64.30	7.345%	$69.0228	$69.02	$69.00	$69.00
Purchase #2	$54.70	9.358%	$59.8188	$59.82	$59.80	$59.80
Purchase #3	$168.51	3.240%	$173.9697	$173.97	$173.95	$174.00
Purchase #4	$83.62	9.458%	$91.5288	$91.53	$91.55	$91.50
Purchase #5	$195.86	4.434%	$204.5444	$204.54	$204.55	$204.50
Purchase #6	$48.86	13.706%	$55.5568	$55.56	$55.55	$55.60
Purchase #7	$31.27	12.802%	$35.2732	$35.27	$35.25	$35.30
7 purchase totals =	$647.12		$689.7145	$689.71	$689.65	$689.70