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	$167.37	8.338%	$181.3253	$181.33	$181.35	$181.30
Purchase #2	$228.85	9.570%	$250.7509	$250.75	$250.75	$250.80
Purchase #3	$223.32	8.498%	$242.2977	$242.30	$242.30	$242.30
Purchase #4	$74.27	4.434%	$77.5631	$77.56	$77.55	$77.60
Purchase #5	$73.81	4.140%	$76.8657	$76.87	$76.85	$76.90
Purchase #6	$89.83	13.581%	$102.0298	$102.03	$102.05	$102.00
Purchase #7	$150.56	9.202%	$164.4145	$164.41	$164.40	$164.40
7 purchase totals =	$1,008.01		$1,095.2470	$1,095.25	$1,095.25	$1,095.30