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	$127.49	12.124%	$142.9469	$142.95	$142.95	$142.90
Purchase #2	$89.51	11.426%	$99.7374	$99.74	$99.75	$99.70
Purchase #3	$150.89	9.186%	$164.7508	$164.75	$164.75	$164.80
Purchase #4	$42.58	11.532%	$47.4903	$47.49	$47.50	$47.50
Purchase #5	$89.85	7.148%	$96.2725	$96.27	$96.25	$96.30
Purchase #6	$142.55	9.722%	$156.4087	$156.41	$156.40	$156.40
Purchase #7	$114.91	6.731%	$122.6446	$122.64	$122.65	$122.60
7 purchase totals =	$757.78		$830.2512	$830.25	$830.25	$830.20