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	$144.64	3.678%	$149.9599	$149.96	$149.95	$150.00
Purchase #2	$147.49	13.645%	$167.615	$167.62	$167.60	$167.60
Purchase #3	$29.66	13.278%	$33.5983	$33.60	$33.60	$33.60
Purchase #4	$98.29	8.326%	$106.4736	$106.47	$106.45	$106.50
Purchase #5	$201.84	10.844%	$223.7275	$223.73	$223.75	$223.70
Purchase #6	$51.44	4.649%	$53.8314	$53.83	$53.85	$53.80
Purchase #7	$92.77	8.770%	$100.9059	$100.91	$100.90	$100.90
7 purchase totals =	$766.13		$836.1116	$836.12	$836.10	$836.10