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	$197.52	13.349%	$223.8869	$223.89	$223.90	$223.90
Purchase #2	$98.83	13.331%	$112.005	$112.01	$112.00	$112.00
Purchase #3	$19.72	5.731%	$20.8502	$20.85	$20.85	$20.90
Purchase #4	$39.82	8.578%	$43.2358	$43.24	$43.25	$43.20
Purchase #5	$245.45	9.741%	$269.3593	$269.36	$269.35	$269.40
Purchase #6	$115.35	3.181%	$119.0193	$119.02	$119.00	$119.00
Purchase #7	$37.26	4.250%	$38.8436	$38.84	$38.85	$38.80
7 purchase totals =	$753.95		$827.2001	$827.21	$827.20	$827.20