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	$197.47	13.175%	$223.4867	$223.49	$223.50	$223.50
Purchase #2	$155.69	3.323%	$160.8636	$160.86	$160.85	$160.90
Purchase #3	$111.91	13.722%	$127.2663	$127.27	$127.25	$127.30
Purchase #4	$100.38	7.148%	$107.5552	$107.56	$107.55	$107.60
Purchase #5	$73.64	9.280%	$80.4738	$80.47	$80.45	$80.50
Purchase #6	$17.28	9.373%	$18.8997	$18.90	$18.90	$18.90
Purchase #7	$249.32	12.569%	$280.657	$280.66	$280.65	$280.70
7 purchase totals =	$905.69		$999.2023	$999.21	$999.15	$999.40