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	$196.90	5.188%	$207.1152	$207.12	$207.10	$207.10
Purchase #2	$134.76	9.318%	$147.3169	$147.32	$147.30	$147.30
Purchase #3	$89.56	11.385%	$99.7564	$99.76	$99.75	$99.80
Purchase #4	$151.74	7.422%	$163.0021	$163.00	$163.00	$163.00
Purchase #5	$19.61	9.617%	$21.4959	$21.50	$21.50	$21.50
Purchase #6	$98.43	7.643%	$105.953	$105.95	$105.95	$106.00
Purchase #7	$127.86	10.406%	$141.1651	$141.17	$141.15	$141.20
7 purchase totals =	$818.86		$885.8046	$885.82	$885.75	$885.90