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	$127.34	12.226%	$142.9086	$142.91	$142.90	$142.90
Purchase #2	$66.48	4.424%	$69.4211	$69.42	$69.40	$69.40
Purchase #3	$135.47	7.541%	$145.6858	$145.69	$145.70	$145.70
Purchase #4	$61.31	10.303%	$67.6268	$67.63	$67.65	$67.60
Purchase #5	$38.86	8.645%	$42.2194	$42.22	$42.20	$42.20
Purchase #6	$28.55	8.677%	$31.0273	$31.03	$31.05	$31.00
Purchase #7	$219.47	6.323%	$233.3471	$233.35	$233.35	$233.30
7 purchase totals =	$677.48		$732.2361	$732.25	$732.25	$732.10