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	$159.77	8.832%	$173.8809	$173.88	$173.90	$173.90
Purchase #2	$102.25	3.238%	$105.5609	$105.56	$105.55	$105.60
Purchase #3	$238.91	4.271%	$249.1138	$249.11	$249.10	$249.10
Purchase #4	$135.78	11.683%	$151.6432	$151.64	$151.65	$151.60
Purchase #5	$200.55	7.801%	$216.1949	$216.19	$216.20	$216.20
Purchase #6	$133.72	4.263%	$139.4205	$139.42	$139.40	$139.40
Purchase #7	$106.43	3.289%	$109.9305	$109.93	$109.95	$109.90
7 purchase totals =	$1,077.41		$1,145.7447	$1,145.73	$1,145.75	$1,145.70