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	$111.28	7.420%	$119.537	$119.54	$119.55	$119.50
Purchase #2	$143.77	11.343%	$160.0778	$160.08	$160.10	$160.10
Purchase #3	$130.41	9.354%	$142.6086	$142.61	$142.60	$142.60
Purchase #4	$43.27	9.674%	$47.4559	$47.46	$47.45	$47.50
Purchase #5	$157.37	4.836%	$164.9804	$164.98	$165.00	$165.00
Purchase #6	$115.76	11.655%	$129.2518	$129.25	$129.25	$129.30
Purchase #7	$98.83	7.162%	$105.9082	$105.91	$105.90	$105.90
7 purchase totals =	$800.69		$869.8197	$869.83	$869.85	$869.90