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	$73.70	3.569%	$76.3304	$76.33	$76.35	$76.30
Purchase #2	$21.25	5.819%	$22.4865	$22.49	$22.50	$22.50
Purchase #3	$115.81	12.455%	$130.2341	$130.23	$130.25	$130.20
Purchase #4	$242.49	3.453%	$250.8632	$250.86	$250.85	$250.90
Purchase #5	$73.37	6.660%	$78.2564	$78.26	$78.25	$78.30
Purchase #6	$85.95	4.478%	$89.7988	$89.80	$89.80	$89.80
Purchase #7	$205.29	3.201%	$211.8613	$211.86	$211.85	$211.90
7 purchase totals =	$817.86		$859.8307	$859.83	$859.85	$859.90