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	$158.52	11.213%	$176.2948	$176.29	$176.30	$176.30
Purchase #2	$163.83	7.532%	$176.1697	$176.17	$176.15	$176.20
Purchase #3	$37.80	13.113%	$42.7567	$42.76	$42.75	$42.80
Purchase #4	$98.56	13.807%	$112.1682	$112.17	$112.15	$112.20
Purchase #5	$185.43	4.870%	$194.4604	$194.46	$194.45	$194.50
Purchase #6	$110.26	5.834%	$116.6926	$116.69	$116.70	$116.70
Purchase #7	$178.32	6.308%	$189.5684	$189.57	$189.55	$189.60
7 purchase totals =	$932.72		$1,008.1108	$1,008.11	$1,008.05	$1,008.30