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	$94.79	5.118%	$99.6414	$99.64	$99.65	$99.60
Purchase #2	$9.57	11.163%	$10.6383	$10.64	$10.65	$10.60
Purchase #3	$88.72	10.634%	$98.1545	$98.15	$98.15	$98.20
Purchase #4	$114.97	7.315%	$123.3801	$123.38	$123.40	$123.40
Purchase #5	$54.69	5.838%	$57.8828	$57.88	$57.90	$57.90
Purchase #6	$28.67	5.724%	$30.3111	$30.31	$30.30	$30.30
Purchase #7	$239.31	11.254%	$266.2419	$266.24	$266.25	$266.20
7 purchase totals =	$630.72		$686.2501	$686.24	$686.30	$686.20