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	$165.44	10.178%	$182.2785	$182.28	$182.30	$182.30
Purchase #2	$35.96	12.527%	$40.4647	$40.46	$40.45	$40.50
Purchase #3	$142.67	9.816%	$156.6745	$156.67	$156.65	$156.70
Purchase #4	$115.29	3.320%	$119.1176	$119.12	$119.10	$119.10
Purchase #5	$45.36	7.534%	$48.7774	$48.78	$48.80	$48.80
Purchase #6	$160.83	7.473%	$172.8488	$172.85	$172.85	$172.80
Purchase #7	$41.96	5.809%	$44.3975	$44.40	$44.40	$44.40
7 purchase totals =	$707.51		$764.5590	$764.56	$764.55	$764.60