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	$94.41	4.241%	$98.4139	$98.41	$98.40	$98.40
Purchase #2	$183.67	13.146%	$207.8153	$207.82	$207.80	$207.80
Purchase #3	$171.49	4.416%	$179.063	$179.06	$179.05	$179.10
Purchase #4	$91.60	4.553%	$95.7705	$95.77	$95.75	$95.80
Purchase #5	$72.90	7.364%	$78.2684	$78.27	$78.25	$78.30
Purchase #6	$95.40	4.656%	$99.8418	$99.84	$99.85	$99.80
Purchase #7	$135.47	3.296%	$139.9351	$139.94	$139.95	$139.90
7 purchase totals =	$844.94		$899.1080	$899.11	$899.05	$899.10