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	$54.41	8.597%	$59.0876	$59.09	$59.10	$59.10
Purchase #2	$19.43	11.861%	$21.7346	$21.73	$21.75	$21.70
Purchase #3	$225.76	7.710%	$243.1661	$243.17	$243.15	$243.20
Purchase #4	$240.79	4.223%	$250.9586	$250.96	$250.95	$251.00
Purchase #5	$53.85	10.825%	$59.6793	$59.68	$59.70	$59.70
Purchase #6	$35.61	4.291%	$37.138	$37.14	$37.15	$37.10
Purchase #7	$29.39	6.731%	$31.3682	$31.37	$31.35	$31.40
7 purchase totals =	$659.24		$703.1324	$703.14	$703.15	$703.20