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	$130.59	5.645%	$137.9618	$137.96	$137.95	$138.00
Purchase #2	$238.95	11.797%	$267.1389	$267.14	$267.15	$267.10
Purchase #3	$56.39	6.268%	$59.9245	$59.92	$59.90	$59.90
Purchase #4	$85.73	11.675%	$95.739	$95.74	$95.75	$95.70
Purchase #5	$83.44	8.851%	$90.8253	$90.83	$90.85	$90.80
Purchase #6	$167.34	12.513%	$188.2793	$188.28	$188.30	$188.30
Purchase #7	$168.95	6.471%	$179.8828	$179.88	$179.90	$179.90
7 purchase totals =	$931.39		$1,019.7516	$1,019.75	$1,019.80	$1,019.70