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	$190.60	3.336%	$196.9584	$196.96	$196.95	$197.00
Purchase #2	$218.43	12.155%	$244.9802	$244.98	$245.00	$245.00
Purchase #3	$39.74	7.692%	$42.7968	$42.80	$42.80	$42.80
Purchase #4	$138.59	3.154%	$142.9611	$142.96	$142.95	$143.00
Purchase #5	$137.62	11.761%	$153.8055	$153.81	$153.80	$153.80
Purchase #6	$19.78	7.615%	$21.2862	$21.29	$21.30	$21.30
Purchase #7	$6.46	13.685%	$7.3441	$7.34	$7.35	$7.30
7 purchase totals =	$751.22		$810.1323	$810.14	$810.15	$810.20