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	$50.32	7.486%	$54.087	$54.09	$54.10	$54.10
Purchase #2	$152.96	9.494%	$167.482	$167.48	$167.50	$167.50
Purchase #3	$184.97	12.569%	$208.2189	$208.22	$208.20	$208.20
Purchase #4	$27.79	6.169%	$29.5044	$29.50	$29.50	$29.50
Purchase #5	$105.90	4.362%	$110.5194	$110.52	$110.50	$110.50
Purchase #6	$148.66	10.734%	$164.6172	$164.62	$164.60	$164.60
Purchase #7	$42.76	8.846%	$46.5425	$46.54	$46.55	$46.50
7 purchase totals =	$713.36		$780.9714	$780.97	$780.95	$780.90