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	$47.63	3.460%	$49.278	$49.28	$49.30	$49.30
Purchase #2	$83.59	8.306%	$90.533	$90.53	$90.55	$90.50
Purchase #3	$170.48	6.104%	$180.8861	$180.89	$180.90	$180.90
Purchase #4	$27.72	3.411%	$28.6655	$28.67	$28.65	$28.70
Purchase #5	$118.25	6.854%	$126.3549	$126.35	$126.35	$126.40
Purchase #6	$39.84	3.826%	$41.3643	$41.36	$41.35	$41.40
Purchase #7	$6.89	13.132%	$7.7948	$7.79	$7.80	$7.80
7 purchase totals =	$494.40		$524.8766	$524.87	$524.90	$525.00