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	$51.96	4.729%	$54.4172	$54.42	$54.40	$54.40
Purchase #2	$164.59	10.665%	$182.1435	$182.14	$182.15	$182.10
Purchase #3	$64.27	11.537%	$71.6848	$71.68	$71.70	$71.70
Purchase #4	$90.51	9.209%	$98.8451	$98.85	$98.85	$98.80
Purchase #5	$85.30	13.573%	$96.8778	$96.88	$96.90	$96.90
Purchase #6	$50.32	11.612%	$56.1632	$56.16	$56.15	$56.20
Purchase #7	$193.50	3.756%	$200.7679	$200.77	$200.75	$200.80
7 purchase totals =	$700.45		$760.8995	$760.90	$760.90	$760.90