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	$47.35	12.861%	$53.4397	$53.44	$53.45	$53.40
Purchase #2	$246.90	5.836%	$261.3091	$261.31	$261.30	$261.30
Purchase #3	$96.65	3.468%	$100.0018	$100.00	$100.00	$100.00
Purchase #4	$238.73	10.699%	$264.2717	$264.27	$264.25	$264.30
Purchase #5	$43.81	6.873%	$46.8211	$46.82	$46.80	$46.80
Purchase #6	$175.25	12.162%	$196.5639	$196.56	$196.55	$196.60
Purchase #7	$154.92	10.121%	$170.5995	$170.60	$170.60	$170.60
7 purchase totals =	$1,003.61		$1,093.0068	$1,093.00	$1,092.95	$1,093.00