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	$140.35	9.236%	$153.3127	$153.31	$153.30	$153.30
Purchase #2	$164.56	9.666%	$180.4664	$180.47	$180.45	$180.50
Purchase #3	$120.37	6.836%	$128.5985	$128.60	$128.60	$128.60
Purchase #4	$173.40	12.319%	$194.7611	$194.76	$194.75	$194.80
Purchase #5	$53.73	10.123%	$59.1691	$59.17	$59.15	$59.20
Purchase #6	$215.56	5.808%	$228.0797	$228.08	$228.10	$228.10
Purchase #7	$89.55	12.501%	$100.7446	$100.74	$100.75	$100.70
7 purchase totals =	$957.52		$1,045.1321	$1,045.13	$1,045.10	$1,045.20