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	$74.48	4.668%	$77.9567	$77.96	$77.95	$78.00
Purchase #2	$40.48	11.738%	$45.2315	$45.23	$45.25	$45.20
Purchase #3	$100.94	13.450%	$114.5164	$114.52	$114.50	$114.50
Purchase #4	$161.25	12.418%	$181.274	$181.27	$181.25	$181.30
Purchase #5	$207.50	4.252%	$216.3229	$216.32	$216.30	$216.30
Purchase #6	$115.73	6.320%	$123.0441	$123.04	$123.05	$123.00
Purchase #7	$229.65	8.545%	$249.2736	$249.27	$249.25	$249.30
7 purchase totals =	$930.03		$1,007.6192	$1,007.61	$1,007.55	$1,007.60