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	$114.28	11.437%	$127.3502	$127.35	$127.35	$127.40
Purchase #2	$239.73	13.713%	$272.6042	$272.60	$272.60	$272.60
Purchase #3	$73.65	7.531%	$79.1966	$79.20	$79.20	$79.20
Purchase #4	$101.46	7.799%	$109.3729	$109.37	$109.35	$109.40
Purchase #5	$48.64	5.751%	$51.4373	$51.44	$51.45	$51.40
Purchase #6	$31.27	7.132%	$33.5002	$33.50	$33.50	$33.50
Purchase #7	$49.62	13.521%	$56.3291	$56.33	$56.35	$56.30
7 purchase totals =	$658.65		$729.7905	$729.79	$729.80	$729.80