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	$52.91	5.187%	$55.6544	$55.65	$55.65	$55.70
Purchase #2	$60.88	5.313%	$64.1146	$64.11	$64.10	$64.10
Purchase #3	$19.41	3.155%	$20.0224	$20.02	$20.00	$20.00
Purchase #4	$91.41	12.440%	$102.7814	$102.78	$102.80	$102.80
Purchase #5	$48.43	12.186%	$54.3317	$54.33	$54.35	$54.30
Purchase #6	$214.59	3.325%	$221.7251	$221.73	$221.75	$221.70
Purchase #7	$162.59	7.382%	$174.5924	$174.59	$174.60	$174.60
7 purchase totals =	$650.22		$693.2220	$693.21	$693.25	$693.20