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	$65.87	10.625%	$72.8687	$72.87	$72.85	$72.90
Purchase #2	$221.39	6.743%	$236.3183	$236.32	$236.30	$236.30
Purchase #3	$153.66	13.613%	$174.5777	$174.58	$174.60	$174.60
Purchase #4	$192.53	13.591%	$218.6968	$218.70	$218.70	$218.70
Purchase #5	$48.91	3.240%	$50.4947	$50.49	$50.50	$50.50
Purchase #6	$28.96	8.393%	$31.3906	$31.39	$31.40	$31.40
Purchase #7	$167.40	10.664%	$185.2515	$185.25	$185.25	$185.30
7 purchase totals =	$878.72		$969.5983	$969.60	$969.60	$969.70