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	$47.73	11.310%	$53.1283	$53.13	$53.15	$53.10
Purchase #2	$18.25	7.512%	$19.6209	$19.62	$19.60	$19.60
Purchase #3	$81.46	10.755%	$90.221	$90.22	$90.20	$90.20
Purchase #4	$121.57	5.410%	$128.1469	$128.15	$128.15	$128.10
Purchase #5	$37.87	12.746%	$42.6969	$42.70	$42.70	$42.70
Purchase #6	$63.95	5.416%	$67.4135	$67.41	$67.40	$67.40
Purchase #7	$86.47	12.417%	$97.207	$97.21	$97.20	$97.20
7 purchase totals =	$457.30		$498.4345	$498.44	$498.40	$498.30