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	$158.32	4.407%	$165.2972	$165.30	$165.30	$165.30
Purchase #2	$112.96	5.513%	$119.1875	$119.19	$119.20	$119.20
Purchase #3	$10.47	12.849%	$11.8153	$11.82	$11.80	$11.80
Purchase #4	$103.50	6.335%	$110.0567	$110.06	$110.05	$110.10
Purchase #5	$156.52	11.285%	$174.1833	$174.18	$174.20	$174.20
Purchase #6	$219.88	11.849%	$245.9336	$245.93	$245.95	$245.90
Purchase #7	$137.40	10.861%	$152.323	$152.32	$152.30	$152.30
7 purchase totals =	$899.05		$978.7966	$978.80	$978.80	$978.80