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	$250.32	12.617%	$281.9029	$281.90	$281.90	$281.90
Purchase #2	$12.72	7.330%	$13.6524	$13.65	$13.65	$13.70
Purchase #3	$51.45	7.707%	$55.4153	$55.42	$55.40	$55.40
Purchase #4	$101.67	4.511%	$106.2563	$106.26	$106.25	$106.30
Purchase #5	$175.57	12.156%	$196.9123	$196.91	$196.90	$196.90
Purchase #6	$132.99	8.501%	$144.2955	$144.30	$144.30	$144.30
Purchase #7	$91.41	11.326%	$101.7631	$101.76	$101.75	$101.80
7 purchase totals =	$816.13		$900.1978	$900.20	$900.15	$900.30