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	$102.57	7.687%	$110.4546	$110.45	$110.45	$110.50
Purchase #2	$120.74	5.650%	$127.5618	$127.56	$127.55	$127.60
Purchase #3	$154.41	5.251%	$162.5181	$162.52	$162.50	$162.50
Purchase #4	$60.31	8.271%	$65.2982	$65.30	$65.30	$65.30
Purchase #5	$115.89	11.404%	$129.1061	$129.11	$129.10	$129.10
Purchase #6	$18.47	12.654%	$20.8072	$20.81	$20.80	$20.80
Purchase #7	$231.43	3.659%	$239.898	$239.90	$239.90	$239.90
7 purchase totals =	$803.82		$855.6440	$855.65	$855.60	$855.70