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	$132.36	6.146%	$140.4948	$140.49	$140.50	$140.50
Purchase #2	$91.92	11.618%	$102.5993	$102.60	$102.60	$102.60
Purchase #3	$230.27	8.679%	$250.2551	$250.26	$250.25	$250.30
Purchase #4	$205.84	6.437%	$219.0899	$219.09	$219.10	$219.10
Purchase #5	$50.74	6.460%	$54.0178	$54.02	$54.00	$54.00
Purchase #6	$200.38	11.631%	$223.6862	$223.69	$223.70	$223.70
Purchase #7	$148.86	3.794%	$154.5077	$154.51	$154.50	$154.50
7 purchase totals =	$1,060.37		$1,144.6508	$1,144.66	$1,144.65	$1,144.70