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	$173.56	10.592%	$191.9435	$191.94	$191.95	$191.90
Purchase #2	$77.87	6.796%	$83.162	$83.16	$83.15	$83.20
Purchase #3	$73.59	11.646%	$82.1603	$82.16	$82.15	$82.20
Purchase #4	$53.72	13.587%	$61.0189	$61.02	$61.00	$61.00
Purchase #5	$206.35	7.274%	$221.3599	$221.36	$221.35	$221.40
Purchase #6	$183.62	7.746%	$197.8432	$197.84	$197.85	$197.80
Purchase #7	$151.73	13.582%	$172.338	$172.34	$172.35	$172.30
7 purchase totals =	$920.44		$1,009.8258	$1,009.82	$1,009.80	$1,009.80