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	$165.55	7.719%	$178.3288	$178.33	$178.35	$178.30
Purchase #2	$85.71	5.121%	$90.0992	$90.10	$90.10	$90.10
Purchase #3	$156.82	9.433%	$171.6128	$171.61	$171.60	$171.60
Purchase #4	$175.66	7.728%	$189.235	$189.24	$189.25	$189.20
Purchase #5	$244.52	4.128%	$254.6138	$254.61	$254.60	$254.60
Purchase #6	$181.82	12.797%	$205.0875	$205.09	$205.10	$205.10
Purchase #7	$77.26	6.103%	$81.9752	$81.98	$82.00	$82.00
7 purchase totals =	$1,087.34		$1,170.9523	$1,170.96	$1,171.00	$1,170.90