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	$243.84	13.542%	$276.8608	$276.86	$276.85	$276.90
Purchase #2	$11.80	4.144%	$12.289	$12.29	$12.30	$12.30
Purchase #3	$82.69	12.355%	$92.9063	$92.91	$92.90	$92.90
Purchase #4	$158.80	6.134%	$168.5408	$168.54	$168.55	$168.50
Purchase #5	$122.71	8.846%	$133.5649	$133.56	$133.55	$133.60
Purchase #6	$229.98	13.649%	$261.37	$261.37	$261.35	$261.40
Purchase #7	$152.90	6.256%	$162.4654	$162.47	$162.45	$162.50
7 purchase totals =	$1,002.72		$1,107.9972	$1,108.00	$1,107.95	$1,108.10