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	$46.40	12.785%	$52.3322	$52.33	$52.35	$52.30
Purchase #2	$198.50	13.789%	$225.8712	$225.87	$225.85	$225.90
Purchase #3	$183.31	4.473%	$191.5095	$191.51	$191.50	$191.50
Purchase #4	$45.69	13.413%	$51.8184	$51.82	$51.80	$51.80
Purchase #5	$229.40	3.449%	$237.312	$237.31	$237.30	$237.30
Purchase #6	$241.53	11.837%	$270.1199	$270.12	$270.10	$270.10
Purchase #7	$112.33	6.527%	$119.6618	$119.66	$119.65	$119.70
7 purchase totals =	$1,057.16		$1,148.6250	$1,148.62	$1,148.55	$1,148.60