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	$100.37	5.569%	$105.9596	$105.96	$105.95	$106.00
Purchase #2	$168.52	13.327%	$190.9787	$190.98	$191.00	$191.00
Purchase #3	$83.45	7.263%	$89.511	$89.51	$89.50	$89.50
Purchase #4	$232.84	10.816%	$258.024	$258.02	$258.00	$258.00
Purchase #5	$140.96	4.585%	$147.423	$147.42	$147.40	$147.40
Purchase #6	$110.55	6.639%	$117.8894	$117.89	$117.90	$117.90
Purchase #7	$141.63	13.767%	$161.1282	$161.13	$161.15	$161.10
7 purchase totals =	$978.32		$1,070.9139	$1,070.91	$1,070.90	$1,070.90