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	$142.75	12.523%	$160.6266	$160.63	$160.65	$160.60
Purchase #2	$231.85	7.626%	$249.5309	$249.53	$249.55	$249.50
Purchase #3	$223.84	13.711%	$254.5307	$254.53	$254.55	$254.50
Purchase #4	$67.51	8.340%	$73.1403	$73.14	$73.15	$73.10
Purchase #5	$109.71	4.332%	$114.4626	$114.46	$114.45	$114.50
Purchase #6	$38.83	9.265%	$42.4276	$42.43	$42.45	$42.40
Purchase #7	$237.69	5.434%	$250.6061	$250.61	$250.60	$250.60
7 purchase totals =	$1,052.18		$1,145.3248	$1,145.33	$1,145.40	$1,145.20