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	$178.76	9.823%	$196.3196	$196.32	$196.30	$196.30
Purchase #2	$103.84	5.792%	$109.8544	$109.85	$109.85	$109.90
Purchase #3	$39.90	5.834%	$42.2278	$42.23	$42.25	$42.20
Purchase #4	$39.33	7.522%	$42.2884	$42.29	$42.30	$42.30
Purchase #5	$29.91	3.581%	$30.9811	$30.98	$31.00	$31.00
Purchase #6	$149.95	11.706%	$167.5031	$167.50	$167.50	$167.50
Purchase #7	$157.96	6.850%	$168.7803	$168.78	$168.80	$168.80
7 purchase totals =	$699.65		$757.9547	$757.95	$758.00	$758.00