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	$150.44	9.375%	$164.5438	$164.54	$164.55	$164.50
Purchase #2	$99.42	7.790%	$107.1648	$107.16	$107.15	$107.20
Purchase #3	$153.61	5.678%	$162.332	$162.33	$162.35	$162.30
Purchase #4	$56.62	9.437%	$61.9632	$61.96	$61.95	$62.00
Purchase #5	$133.43	4.533%	$139.4784	$139.48	$139.50	$139.50
Purchase #6	$51.91	5.696%	$54.8668	$54.87	$54.85	$54.90
Purchase #7	$31.26	4.836%	$32.7717	$32.77	$32.75	$32.80
7 purchase totals =	$676.69		$723.1207	$723.11	$723.10	$723.20