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	$9.89	10.539%	$10.9323	$10.93	$10.95	$10.90
Purchase #2	$59.76	8.149%	$64.6298	$64.63	$64.65	$64.60
Purchase #3	$56.39	5.618%	$59.558	$59.56	$59.55	$59.60
Purchase #4	$123.47	3.347%	$127.6025	$127.60	$127.60	$127.60
Purchase #5	$210.30	11.322%	$234.1102	$234.11	$234.10	$234.10
Purchase #6	$91.34	10.441%	$100.8768	$100.88	$100.90	$100.90
Purchase #7	$88.57	11.291%	$98.5704	$98.57	$98.55	$98.60
7 purchase totals =	$639.72		$696.2800	$696.28	$696.30	$696.30