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	$99.87	11.746%	$111.6007	$111.60	$111.60	$111.60
Purchase #2	$164.48	9.785%	$180.5744	$180.57	$180.55	$180.60
Purchase #3	$205.42	3.795%	$213.2157	$213.22	$213.20	$213.20
Purchase #4	$229.56	8.395%	$248.8316	$248.83	$248.85	$248.80
Purchase #5	$161.40	8.786%	$175.5806	$175.58	$175.60	$175.60
Purchase #6	$104.43	6.399%	$111.1125	$111.11	$111.10	$111.10
Purchase #7	$250.39	6.577%	$266.8582	$266.86	$266.85	$266.90
7 purchase totals =	$1,215.55		$1,307.7737	$1,307.77	$1,307.75	$1,307.80