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	$137.59	5.404%	$145.0254	$145.03	$145.05	$145.00
Purchase #2	$32.51	13.844%	$37.0107	$37.01	$37.00	$37.00
Purchase #3	$91.39	9.379%	$99.9615	$99.96	$99.95	$100.00
Purchase #4	$54.32	9.343%	$59.3951	$59.40	$59.40	$59.40
Purchase #5	$28.56	3.542%	$29.5716	$29.57	$29.55	$29.60
Purchase #6	$230.28	13.449%	$261.2504	$261.25	$261.25	$261.30
Purchase #7	$27.25	9.113%	$29.7333	$29.73	$29.75	$29.70
7 purchase totals =	$601.90		$661.9480	$661.95	$661.95	$662.00