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	$48.42	7.306%	$51.9576	$51.96	$51.95	$52.00
Purchase #2	$96.51	3.859%	$100.2343	$100.23	$100.25	$100.20
Purchase #3	$54.62	8.815%	$59.4348	$59.43	$59.45	$59.40
Purchase #4	$97.47	13.535%	$110.6626	$110.66	$110.65	$110.70
Purchase #5	$145.67	4.476%	$152.1902	$152.19	$152.20	$152.20
Purchase #6	$187.54	8.850%	$204.1373	$204.14	$204.15	$204.10
Purchase #7	$97.59	5.257%	$102.7203	$102.72	$102.70	$102.70
7 purchase totals =	$727.82		$781.3371	$781.33	$781.35	$781.30