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	$47.92	12.420%	$53.8717	$53.87	$53.85	$53.90
Purchase #2	$96.96	9.260%	$105.9385	$105.94	$105.95	$105.90
Purchase #3	$63.28	9.532%	$69.3118	$69.31	$69.30	$69.30
Purchase #4	$30.67	4.640%	$32.0931	$32.09	$32.10	$32.10
Purchase #5	$85.27	4.747%	$89.3178	$89.32	$89.30	$89.30
Purchase #6	$80.63	12.391%	$90.6209	$90.62	$90.60	$90.60
Purchase #7	$111.78	3.321%	$115.4922	$115.49	$115.50	$115.50
7 purchase totals =	$516.51		$556.6460	$556.64	$556.60	$556.60