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	$149.98	8.220%	$162.3084	$162.31	$162.30	$162.30
Purchase #2	$222.94	9.217%	$243.4884	$243.49	$243.50	$243.50
Purchase #3	$200.74	6.385%	$213.5572	$213.56	$213.55	$213.60
Purchase #4	$74.93	4.603%	$78.379	$78.38	$78.40	$78.40
Purchase #5	$165.52	3.655%	$171.5698	$171.57	$171.55	$171.60
Purchase #6	$195.96	10.405%	$216.3496	$216.35	$216.35	$216.30
Purchase #7	$199.59	3.446%	$206.4679	$206.47	$206.45	$206.50
7 purchase totals =	$1,209.66		$1,292.1203	$1,292.13	$1,292.10	$1,292.20