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	$204.65	7.196%	$219.3766	$219.38	$219.40	$219.40
Purchase #2	$144.77	6.610%	$154.3393	$154.34	$154.35	$154.30
Purchase #3	$189.69	3.507%	$196.3424	$196.34	$196.35	$196.30
Purchase #4	$110.25	3.450%	$114.0536	$114.05	$114.05	$114.10
Purchase #5	$202.26	7.673%	$217.7794	$217.78	$217.80	$217.80
Purchase #6	$151.29	7.648%	$162.8607	$162.86	$162.85	$162.90
Purchase #7	$77.47	13.588%	$87.9966	$88.00	$88.00	$88.00
7 purchase totals =	$1,080.38		$1,152.7486	$1,152.75	$1,152.80	$1,152.80