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	$178.28	11.562%	$198.8927	$198.89	$198.90	$198.90
Purchase #2	$44.25	4.834%	$46.389	$46.39	$46.40	$46.40
Purchase #3	$133.44	8.309%	$144.5275	$144.53	$144.55	$144.50
Purchase #4	$121.67	11.152%	$135.2386	$135.24	$135.25	$135.20
Purchase #5	$77.90	7.275%	$83.5672	$83.57	$83.55	$83.60
Purchase #6	$67.77	13.242%	$76.7441	$76.74	$76.75	$76.70
Purchase #7	$53.56	11.814%	$59.8876	$59.89	$59.90	$59.90
7 purchase totals =	$676.87		$745.2467	$745.25	$745.30	$745.20