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	$72.75	6.532%	$77.502	$77.50	$77.50	$77.50
Purchase #2	$30.97	9.219%	$33.8251	$33.83	$33.85	$33.80
Purchase #3	$40.38	8.307%	$43.7344	$43.73	$43.75	$43.70
Purchase #4	$188.39	4.214%	$196.3288	$196.33	$196.35	$196.30
Purchase #5	$63.39	5.697%	$67.0013	$67.00	$67.00	$67.00
Purchase #6	$137.81	11.236%	$153.2943	$153.29	$153.30	$153.30
Purchase #7	$211.40	10.299%	$233.1721	$233.17	$233.15	$233.20
7 purchase totals =	$745.09		$804.8580	$804.85	$804.90	$804.80