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	$141.62	4.443%	$147.9122	$147.91	$147.90	$147.90
Purchase #2	$51.69	13.838%	$58.8429	$58.84	$58.85	$58.80
Purchase #3	$105.28	3.708%	$109.1838	$109.18	$109.20	$109.20
Purchase #4	$48.48	6.215%	$51.493	$51.49	$51.50	$51.50
Purchase #5	$159.87	7.501%	$171.8618	$171.86	$171.85	$171.90
Purchase #6	$92.59	6.118%	$98.2547	$98.25	$98.25	$98.30
Purchase #7	$76.52	12.629%	$86.1837	$86.18	$86.20	$86.20
7 purchase totals =	$676.05		$723.7321	$723.71	$723.75	$723.80