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	$117.33	5.183%	$123.4112	$123.41	$123.40	$123.40
Purchase #2	$56.94	4.476%	$59.4886	$59.49	$59.50	$59.50
Purchase #3	$108.60	7.720%	$116.9839	$116.98	$117.00	$117.00
Purchase #4	$64.87	12.479%	$72.9651	$72.97	$72.95	$73.00
Purchase #5	$8.51	12.810%	$9.6001	$9.60	$9.60	$9.60
Purchase #6	$106.74	9.277%	$116.6423	$116.64	$116.65	$116.60
Purchase #7	$200.32	11.333%	$223.0223	$223.02	$223.00	$223.00
7 purchase totals =	$663.31		$722.1135	$722.11	$722.10	$722.10