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	$46.49	7.567%	$50.0079	$50.01	$50.00	$50.00
Purchase #2	$219.31	12.802%	$247.3861	$247.39	$247.40	$247.40
Purchase #3	$190.70	6.309%	$202.7313	$202.73	$202.75	$202.70
Purchase #4	$90.32	7.507%	$97.1003	$97.10	$97.10	$97.10
Purchase #5	$178.46	11.695%	$199.3309	$199.33	$199.35	$199.30
Purchase #6	$240.50	4.321%	$250.892	$250.89	$250.90	$250.90
Purchase #7	$85.52	4.742%	$89.5754	$89.58	$89.60	$89.60
7 purchase totals =	$1,051.30		$1,137.0239	$1,137.03	$1,137.10	$1,137.00