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	$141.90	7.298%	$152.2559	$152.26	$152.25	$152.30
Purchase #2	$99.54	9.584%	$109.0799	$109.08	$109.10	$109.10
Purchase #3	$80.85	12.695%	$91.1139	$91.11	$91.10	$91.10
Purchase #4	$148.76	4.224%	$155.0436	$155.04	$155.05	$155.00
Purchase #5	$144.50	5.124%	$151.9042	$151.90	$151.90	$151.90
Purchase #6	$182.25	7.194%	$195.3611	$195.36	$195.35	$195.40
Purchase #7	$181.99	4.722%	$190.5836	$190.58	$190.60	$190.60
7 purchase totals =	$979.79		$1,045.3422	$1,045.33	$1,045.35	$1,045.40