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	$65.32	4.244%	$68.0922	$68.09	$68.10	$68.10
Purchase #2	$18.34	8.376%	$19.8762	$19.88	$19.90	$19.90
Purchase #3	$133.62	4.266%	$139.3202	$139.32	$139.30	$139.30
Purchase #4	$114.40	11.123%	$127.1247	$127.12	$127.10	$127.10
Purchase #5	$222.38	7.223%	$238.4425	$238.44	$238.45	$238.40
Purchase #6	$178.55	6.335%	$189.8611	$189.86	$189.85	$189.90
Purchase #7	$52.34	4.773%	$54.8382	$54.84	$54.85	$54.80
7 purchase totals =	$784.95		$837.5551	$837.55	$837.55	$837.50