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	$188.31	9.557%	$206.3068	$206.31	$206.30	$206.30
Purchase #2	$190.84	4.755%	$199.9144	$199.91	$199.90	$199.90
Purchase #3	$154.26	11.216%	$171.5618	$171.56	$171.55	$171.60
Purchase #4	$20.84	6.549%	$22.2048	$22.20	$22.20	$22.20
Purchase #5	$162.31	3.414%	$167.8513	$167.85	$167.85	$167.90
Purchase #6	$122.34	6.675%	$130.5062	$130.51	$130.50	$130.50
Purchase #7	$154.88	5.177%	$162.8981	$162.90	$162.90	$162.90
7 purchase totals =	$993.78		$1,061.2434	$1,061.24	$1,061.20	$1,061.30