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	$207.26	10.654%	$229.3415	$229.34	$229.35	$229.30
Purchase #2	$244.83	11.704%	$273.4849	$273.48	$273.50	$273.50
Purchase #3	$19.28	5.359%	$20.3132	$20.31	$20.30	$20.30
Purchase #4	$137.59	11.114%	$152.8818	$152.88	$152.90	$152.90
Purchase #5	$128.90	10.402%	$142.3082	$142.31	$142.30	$142.30
Purchase #6	$101.25	4.593%	$105.9004	$105.90	$105.90	$105.90
Purchase #7	$228.54	5.370%	$240.8126	$240.81	$240.80	$240.80
7 purchase totals =	$1,067.65		$1,165.0426	$1,165.03	$1,165.05	$1,165.00