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	$243.95	9.801%	$267.8595	$267.86	$267.85	$267.90
Purchase #2	$180.27	4.803%	$188.9284	$188.93	$188.95	$188.90
Purchase #3	$130.68	5.555%	$137.9393	$137.94	$137.95	$137.90
Purchase #4	$179.43	6.295%	$190.7251	$190.73	$190.75	$190.70
Purchase #5	$41.72	11.498%	$46.517	$46.52	$46.50	$46.50
Purchase #6	$95.37	3.419%	$98.6307	$98.63	$98.65	$98.60
Purchase #7	$229.61	5.307%	$241.7954	$241.80	$241.80	$241.80
7 purchase totals =	$1,101.03		$1,172.3954	$1,172.41	$1,172.45	$1,172.30