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	$59.43	9.687%	$65.187	$65.19	$65.20	$65.20
Purchase #2	$94.29	7.219%	$101.0968	$101.10	$101.10	$101.10
Purchase #3	$64.91	6.681%	$69.2466	$69.25	$69.25	$69.20
Purchase #4	$25.86	6.391%	$27.5127	$27.51	$27.50	$27.50
Purchase #5	$119.82	6.508%	$127.6179	$127.62	$127.60	$127.60
Purchase #6	$151.66	4.764%	$158.8851	$158.89	$158.90	$158.90
Purchase #7	$223.39	4.359%	$233.1276	$233.13	$233.15	$233.10
7 purchase totals =	$739.36		$782.6737	$782.69	$782.70	$782.60