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	$186.79	13.415%	$211.8479	$211.85	$211.85	$211.80
Purchase #2	$237.78	13.367%	$269.5641	$269.56	$269.55	$269.60
Purchase #3	$153.52	12.857%	$173.2581	$173.26	$173.25	$173.30
Purchase #4	$29.34	4.146%	$30.5564	$30.56	$30.55	$30.60
Purchase #5	$165.36	9.745%	$181.4743	$181.47	$181.45	$181.50
Purchase #6	$130.38	9.476%	$142.7348	$142.73	$142.75	$142.70
Purchase #7	$20.29	7.856%	$21.884	$21.88	$21.90	$21.90
7 purchase totals =	$923.46		$1,031.3196	$1,031.31	$1,031.30	$1,031.40