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	$149.68	4.817%	$156.8901	$156.89	$156.90	$156.90
Purchase #2	$178.71	9.839%	$196.2933	$196.29	$196.30	$196.30
Purchase #3	$69.69	6.623%	$74.3056	$74.31	$74.30	$74.30
Purchase #4	$150.96	11.393%	$168.1589	$168.16	$168.15	$168.20
Purchase #5	$53.44	11.614%	$59.6465	$59.65	$59.65	$59.60
Purchase #6	$143.48	9.288%	$156.8064	$156.81	$156.80	$156.80
Purchase #7	$161.41	12.400%	$181.4248	$181.42	$181.40	$181.40
7 purchase totals =	$907.37		$993.5256	$993.53	$993.50	$993.50