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	$56.32	5.838%	$59.608	$59.61	$59.60	$59.60
Purchase #2	$232.51	4.592%	$243.1869	$243.19	$243.20	$243.20
Purchase #3	$83.63	7.256%	$89.6982	$89.70	$89.70	$89.70
Purchase #4	$147.85	5.519%	$156.0098	$156.01	$156.00	$156.00
Purchase #5	$81.85	11.526%	$91.284	$91.28	$91.30	$91.30
Purchase #6	$217.70	9.511%	$238.4054	$238.41	$238.40	$238.40
Purchase #7	$170.56	9.146%	$186.1594	$186.16	$186.15	$186.20
7 purchase totals =	$990.42		$1,064.3517	$1,064.36	$1,064.35	$1,064.40