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	$206.88	12.675%	$233.102	$233.10	$233.10	$233.10
Purchase #2	$136.73	5.248%	$143.9056	$143.91	$143.90	$143.90
Purchase #3	$158.85	12.524%	$178.7444	$178.74	$178.75	$178.70
Purchase #4	$68.48	7.359%	$73.5194	$73.52	$73.50	$73.50
Purchase #5	$141.61	6.700%	$151.0979	$151.10	$151.10	$151.10
Purchase #6	$122.35	12.658%	$137.8371	$137.84	$137.85	$137.80
Purchase #7	$181.60	10.549%	$200.757	$200.76	$200.75	$200.80
7 purchase totals =	$1,016.50		$1,118.9634	$1,118.97	$1,118.95	$1,118.90