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	$151.34	9.665%	$165.967	$165.97	$165.95	$166.00
Purchase #2	$166.29	4.861%	$174.3734	$174.37	$174.35	$174.40
Purchase #3	$103.46	3.816%	$107.408	$107.41	$107.40	$107.40
Purchase #4	$150.54	4.306%	$157.0223	$157.02	$157.00	$157.00
Purchase #5	$81.26	10.590%	$89.8654	$89.87	$89.85	$89.90
Purchase #6	$43.25	4.751%	$45.3048	$45.30	$45.30	$45.30
Purchase #7	$89.75	6.362%	$95.4599	$95.46	$95.45	$95.50
7 purchase totals =	$785.89		$835.4008	$835.40	$835.30	$835.50