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	$127.53	3.273%	$131.7041	$131.70	$131.70	$131.70
Purchase #2	$26.48	9.390%	$28.9665	$28.97	$28.95	$29.00
Purchase #3	$27.36	3.737%	$28.3824	$28.38	$28.40	$28.40
Purchase #4	$155.87	7.290%	$167.2329	$167.23	$167.25	$167.20
Purchase #5	$91.46	8.680%	$99.3987	$99.40	$99.40	$99.40
Purchase #6	$147.60	6.834%	$157.687	$157.69	$157.70	$157.70
Purchase #7	$185.59	3.209%	$191.5456	$191.55	$191.55	$191.50
7 purchase totals =	$761.89		$804.9172	$804.92	$804.95	$804.90