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	$18.25	6.581%	$19.451	$19.45	$19.45	$19.50
Purchase #2	$11.72	5.229%	$12.3328	$12.33	$12.35	$12.30
Purchase #3	$223.33	12.782%	$251.876	$251.88	$251.90	$251.90
Purchase #4	$77.81	11.412%	$86.6897	$86.69	$86.70	$86.70
Purchase #5	$91.25	12.258%	$102.4354	$102.44	$102.45	$102.40
Purchase #6	$82.58	8.614%	$89.6934	$89.69	$89.70	$89.70
Purchase #7	$194.71	12.484%	$219.0176	$219.02	$219.00	$219.00
7 purchase totals =	$699.65		$781.4959	$781.50	$781.55	$781.50