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	$24.36	5.649%	$25.7361	$25.74	$25.75	$25.70
Purchase #2	$201.25	13.666%	$228.7528	$228.75	$228.75	$228.80
Purchase #3	$56.92	7.822%	$61.3723	$61.37	$61.35	$61.40
Purchase #4	$52.82	3.244%	$54.5335	$54.53	$54.55	$54.50
Purchase #5	$75.58	7.367%	$81.148	$81.15	$81.15	$81.10
Purchase #6	$176.80	11.123%	$196.4655	$196.47	$196.45	$196.50
Purchase #7	$245.54	3.261%	$253.5471	$253.55	$253.55	$253.50
7 purchase totals =	$833.27		$901.5553	$901.56	$901.55	$901.50