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	$162.25	6.471%	$172.7492	$172.75	$172.75	$172.70
Purchase #2	$94.89	9.384%	$103.7945	$103.79	$103.80	$103.80
Purchase #3	$129.37	7.690%	$139.3186	$139.32	$139.30	$139.30
Purchase #4	$53.56	6.460%	$57.02	$57.02	$57.00	$57.00
Purchase #5	$223.54	10.443%	$246.8843	$246.88	$246.90	$246.90
Purchase #6	$177.90	13.300%	$201.5607	$201.56	$201.55	$201.60
Purchase #7	$193.83	6.451%	$206.334	$206.33	$206.35	$206.30
7 purchase totals =	$1,035.34		$1,127.6613	$1,127.65	$1,127.65	$1,127.60