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	$76.95	5.106%	$80.8791	$80.88	$80.90	$80.90
Purchase #2	$116.91	8.730%	$127.1162	$127.12	$127.10	$127.10
Purchase #3	$41.95	7.303%	$45.0136	$45.01	$45.00	$45.00
Purchase #4	$167.77	8.776%	$182.4935	$182.49	$182.50	$182.50
Purchase #5	$58.59	13.567%	$66.5389	$66.54	$66.55	$66.50
Purchase #6	$178.79	3.805%	$185.593	$185.59	$185.60	$185.60
Purchase #7	$64.43	13.674%	$73.2402	$73.24	$73.25	$73.20
7 purchase totals =	$705.39		$760.8745	$760.87	$760.90	$760.80