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	$128.88	10.325%	$142.1869	$142.19	$142.20	$142.20
Purchase #2	$80.43	11.764%	$89.8918	$89.89	$89.90	$89.90
Purchase #3	$101.30	5.168%	$106.5352	$106.54	$106.55	$106.50
Purchase #4	$200.64	11.736%	$224.1871	$224.19	$224.20	$224.20
Purchase #5	$179.77	13.848%	$204.6645	$204.66	$204.65	$204.70
Purchase #6	$80.43	6.167%	$85.3901	$85.39	$85.40	$85.40
Purchase #7	$199.77	11.119%	$221.9824	$221.98	$222.00	$222.00
7 purchase totals =	$971.22		$1,074.8380	$1,074.84	$1,074.90	$1,074.90