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	$141.49	4.477%	$147.8245	$147.82	$147.80	$147.80
Purchase #2	$217.96	12.813%	$245.8872	$245.89	$245.90	$245.90
Purchase #3	$126.91	3.356%	$131.1691	$131.17	$131.15	$131.20
Purchase #4	$17.36	8.625%	$18.8573	$18.86	$18.85	$18.90
Purchase #5	$39.53	11.498%	$44.0752	$44.08	$44.10	$44.10
Purchase #6	$29.89	4.769%	$31.3155	$31.32	$31.30	$31.30
Purchase #7	$83.74	3.196%	$86.4163	$86.42	$86.40	$86.40
7 purchase totals =	$656.88		$705.5451	$705.56	$705.50	$705.60