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	$99.36	13.837%	$113.1084	$113.11	$113.10	$113.10
Purchase #2	$47.84	4.628%	$50.054	$50.05	$50.05	$50.10
Purchase #3	$158.98	4.253%	$165.7414	$165.74	$165.75	$165.70
Purchase #4	$34.86	4.790%	$36.5298	$36.53	$36.55	$36.50
Purchase #5	$109.35	13.298%	$123.8914	$123.89	$123.90	$123.90
Purchase #6	$27.27	4.121%	$28.3938	$28.39	$28.40	$28.40
Purchase #7	$150.37	9.239%	$164.2627	$164.26	$164.25	$164.30
7 purchase totals =	$628.03		$681.9815	$681.97	$682.00	$682.00