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	$148.74	10.779%	$164.7727	$164.77	$164.75	$164.80
Purchase #2	$77.75	9.514%	$85.1471	$85.15	$85.15	$85.10
Purchase #3	$80.63	6.360%	$85.7581	$85.76	$85.75	$85.80
Purchase #4	$89.35	10.244%	$98.503	$98.50	$98.50	$98.50
Purchase #5	$233.76	13.224%	$264.6724	$264.67	$264.65	$264.70
Purchase #6	$227.76	11.440%	$253.8157	$253.82	$253.80	$253.80
Purchase #7	$221.89	13.547%	$251.9494	$251.95	$251.95	$251.90
7 purchase totals =	$1,079.88		$1,204.6184	$1,204.62	$1,204.55	$1,204.60