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	$149.89	8.146%	$162.1	$162.10	$162.10	$162.10
Purchase #2	$162.78	5.430%	$171.619	$171.62	$171.60	$171.60
Purchase #3	$47.91	10.416%	$52.9003	$52.90	$52.90	$52.90
Purchase #4	$163.39	4.752%	$171.1543	$171.15	$171.15	$171.20
Purchase #5	$89.75	10.419%	$99.1011	$99.10	$99.10	$99.10
Purchase #6	$166.48	9.386%	$182.1058	$182.11	$182.10	$182.10
Purchase #7	$179.63	5.455%	$189.4288	$189.43	$189.45	$189.40
7 purchase totals =	$959.83		$1,028.4093	$1,028.41	$1,028.40	$1,028.40