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	$162.73	7.202%	$174.4498	$174.45	$174.45	$174.40
Purchase #2	$109.50	4.171%	$114.0672	$114.07	$114.05	$114.10
Purchase #3	$47.27	13.755%	$53.772	$53.77	$53.75	$53.80
Purchase #4	$45.94	11.645%	$51.2897	$51.29	$51.30	$51.30
Purchase #5	$145.99	13.525%	$165.7351	$165.74	$165.75	$165.70
Purchase #6	$139.86	4.168%	$145.6894	$145.69	$145.70	$145.70
Purchase #7	$209.47	9.274%	$228.8962	$228.90	$228.90	$228.90
7 purchase totals =	$860.76		$933.8994	$933.91	$933.90	$933.90