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	$65.30	3.119%	$67.3367	$67.34	$67.35	$67.30
Purchase #2	$43.31	4.668%	$45.3317	$45.33	$45.35	$45.30
Purchase #3	$227.98	10.415%	$251.7241	$251.72	$251.70	$251.70
Purchase #4	$148.27	10.619%	$164.0148	$164.01	$164.00	$164.00
Purchase #5	$80.88	9.144%	$88.2757	$88.28	$88.30	$88.30
Purchase #6	$14.95	4.628%	$15.6419	$15.64	$15.65	$15.60
Purchase #7	$105.55	13.713%	$120.0241	$120.02	$120.00	$120.00
7 purchase totals =	$686.24		$752.3490	$752.34	$752.35	$752.20