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	$42.37	6.155%	$44.9779	$44.98	$45.00	$45.00
Purchase #2	$26.50	7.447%	$28.4735	$28.47	$28.45	$28.50
Purchase #3	$35.84	3.492%	$37.0915	$37.09	$37.10	$37.10
Purchase #4	$218.32	12.119%	$244.7782	$244.78	$244.80	$244.80
Purchase #5	$191.65	12.832%	$216.2425	$216.24	$216.25	$216.20
Purchase #6	$231.85	5.228%	$243.9711	$243.97	$243.95	$244.00
Purchase #7	$219.52	13.808%	$249.8313	$249.83	$249.85	$249.80
7 purchase totals =	$966.05		$1,065.3660	$1,065.36	$1,065.40	$1,065.40