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	$25.36	11.555%	$28.2903	$28.29	$28.30	$28.30
Purchase #2	$76.60	3.730%	$79.4572	$79.46	$79.45	$79.50
Purchase #3	$101.39	9.771%	$111.2968	$111.30	$111.30	$111.30
Purchase #4	$211.63	11.150%	$235.2267	$235.23	$235.25	$235.20
Purchase #5	$221.66	6.820%	$236.7772	$236.78	$236.80	$236.80
Purchase #6	$60.70	11.177%	$67.4844	$67.48	$67.50	$67.50
Purchase #7	$110.84	11.765%	$123.8803	$123.88	$123.90	$123.90
7 purchase totals =	$808.18		$882.4129	$882.42	$882.50	$882.50