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	$226.35	9.581%	$248.0366	$248.04	$248.05	$248.00
Purchase #2	$236.52	10.546%	$261.4634	$261.46	$261.45	$261.50
Purchase #3	$46.63	10.819%	$51.6749	$51.67	$51.65	$51.70
Purchase #4	$86.47	5.137%	$90.912	$90.91	$90.90	$90.90
Purchase #5	$110.88	13.416%	$125.7557	$125.76	$125.75	$125.80
Purchase #6	$181.41	4.219%	$189.0637	$189.06	$189.05	$189.10
Purchase #7	$42.27	8.550%	$45.8841	$45.88	$45.90	$45.90
7 purchase totals =	$930.53		$1,012.7904	$1,012.78	$1,012.75	$1,012.90