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	$148.56	8.342%	$160.9529	$160.95	$160.95	$161.00
Purchase #2	$213.89	4.549%	$223.6199	$223.62	$223.60	$223.60
Purchase #3	$86.47	5.140%	$90.9146	$90.91	$90.90	$90.90
Purchase #4	$134.76	6.565%	$143.607	$143.61	$143.60	$143.60
Purchase #5	$129.52	9.123%	$141.3361	$141.34	$141.35	$141.30
Purchase #6	$61.36	9.116%	$66.9536	$66.95	$66.95	$67.00
Purchase #7	$183.61	4.374%	$191.6411	$191.64	$191.65	$191.60
7 purchase totals =	$958.17		$1,019.0252	$1,019.02	$1,019.00	$1,019.00