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	$168.49	9.809%	$185.0172	$185.02	$185.00	$185.00
Purchase #2	$96.39	10.690%	$106.6941	$106.69	$106.70	$106.70
Purchase #3	$213.93	12.195%	$240.0188	$240.02	$240.00	$240.00
Purchase #4	$19.30	4.725%	$20.2119	$20.21	$20.20	$20.20
Purchase #5	$225.41	3.606%	$233.5383	$233.54	$233.55	$233.50
Purchase #6	$83.62	7.363%	$89.7769	$89.78	$89.80	$89.80
Purchase #7	$130.31	13.196%	$147.5057	$147.51	$147.50	$147.50
7 purchase totals =	$937.45		$1,022.7629	$1,022.77	$1,022.75	$1,022.70