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	$117.64	8.301%	$127.4053	$127.41	$127.40	$127.40
Purchase #2	$250.42	11.814%	$280.0046	$280.00	$280.00	$280.00
Purchase #3	$248.28	10.655%	$274.7342	$274.73	$274.75	$274.70
Purchase #4	$57.57	5.510%	$60.7421	$60.74	$60.75	$60.70
Purchase #5	$171.40	10.854%	$190.0038	$190.00	$190.00	$190.00
Purchase #6	$72.67	8.194%	$78.6246	$78.62	$78.60	$78.60
Purchase #7	$32.61	3.138%	$33.6333	$33.63	$33.65	$33.60
7 purchase totals =	$950.59		$1,045.1479	$1,045.13	$1,045.15	$1,045.00