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	$95.49	3.667%	$98.9916	$98.99	$99.00	$99.00
Purchase #2	$130.78	7.307%	$140.3361	$140.34	$140.35	$140.30
Purchase #3	$75.71	6.661%	$80.753	$80.75	$80.75	$80.80
Purchase #4	$43.51	4.179%	$45.3283	$45.33	$45.35	$45.30
Purchase #5	$244.72	11.800%	$273.597	$273.60	$273.60	$273.60
Purchase #6	$167.46	3.517%	$173.3496	$173.35	$173.35	$173.30
Purchase #7	$218.34	6.499%	$232.5299	$232.53	$232.55	$232.50
7 purchase totals =	$976.01		$1,044.8855	$1,044.89	$1,044.95	$1,044.80