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	$40.89	3.465%	$42.3068	$42.31	$42.30	$42.30
Purchase #2	$219.48	10.732%	$243.0346	$243.03	$243.05	$243.00
Purchase #3	$86.63	6.623%	$92.3675	$92.37	$92.35	$92.40
Purchase #4	$235.98	5.767%	$249.589	$249.59	$249.60	$249.60
Purchase #5	$118.90	10.462%	$131.3393	$131.34	$131.35	$131.30
Purchase #6	$17.40	8.692%	$18.9124	$18.91	$18.90	$18.90
Purchase #7	$236.46	3.596%	$244.9631	$244.96	$244.95	$245.00
7 purchase totals =	$955.74		$1,022.5127	$1,022.51	$1,022.50	$1,022.50