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	$87.30	6.420%	$92.9047	$92.90	$92.90	$92.90
Purchase #2	$133.33	12.793%	$150.3869	$150.39	$150.40	$150.40
Purchase #3	$71.88	5.438%	$75.7888	$75.79	$75.80	$75.80
Purchase #4	$163.42	13.207%	$185.0029	$185.00	$185.00	$185.00
Purchase #5	$171.35	10.665%	$189.6245	$189.62	$189.60	$189.60
Purchase #6	$194.56	5.160%	$204.5993	$204.60	$204.60	$204.60
Purchase #7	$159.83	5.136%	$168.0389	$168.04	$168.05	$168.00
7 purchase totals =	$981.67		$1,066.3460	$1,066.34	$1,066.35	$1,066.30