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	$130.68	8.752%	$142.1171	$142.12	$142.10	$142.10
Purchase #2	$241.79	11.150%	$268.7496	$268.75	$268.75	$268.70
Purchase #3	$36.27	9.411%	$39.6834	$39.68	$39.70	$39.70
Purchase #4	$78.71	4.789%	$82.4794	$82.48	$82.50	$82.50
Purchase #5	$162.82	7.190%	$174.5268	$174.53	$174.55	$174.50
Purchase #6	$176.31	13.503%	$200.1171	$200.12	$200.10	$200.10
Purchase #7	$234.86	10.843%	$260.3259	$260.33	$260.35	$260.30
7 purchase totals =	$1,061.44		$1,167.9993	$1,168.01	$1,168.05	$1,167.90