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	$47.95	10.578%	$53.0222	$53.02	$53.00	$53.00
Purchase #2	$132.56	13.689%	$150.7061	$150.71	$150.70	$150.70
Purchase #3	$221.70	11.765%	$247.783	$247.78	$247.80	$247.80
Purchase #4	$100.50	3.394%	$103.911	$103.91	$103.90	$103.90
Purchase #5	$5.99	9.343%	$6.5496	$6.55	$6.55	$6.50
Purchase #6	$82.50	12.153%	$92.5262	$92.53	$92.55	$92.50
Purchase #7	$150.47	9.562%	$164.8579	$164.86	$164.85	$164.90
7 purchase totals =	$741.67		$819.3560	$819.36	$819.35	$819.30