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	$55.26	7.325%	$59.3078	$59.31	$59.30	$59.30
Purchase #2	$92.73	3.587%	$96.0562	$96.06	$96.05	$96.10
Purchase #3	$55.45	7.124%	$59.4003	$59.40	$59.40	$59.40
Purchase #4	$73.45	7.260%	$78.7825	$78.78	$78.80	$78.80
Purchase #5	$64.99	6.585%	$69.2696	$69.27	$69.25	$69.30
Purchase #6	$150.88	9.539%	$165.2724	$165.27	$165.25	$165.30
Purchase #7	$162.81	5.103%	$171.1182	$171.12	$171.10	$171.10
7 purchase totals =	$655.57		$699.2070	$699.21	$699.15	$699.30