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	$168.26	11.133%	$186.9924	$186.99	$187.00	$187.00
Purchase #2	$150.61	4.591%	$157.5245	$157.52	$157.50	$157.50
Purchase #3	$89.44	12.779%	$100.8695	$100.87	$100.85	$100.90
Purchase #4	$165.72	13.658%	$188.354	$188.35	$188.35	$188.40
Purchase #5	$112.28	12.873%	$126.7338	$126.73	$126.75	$126.70
Purchase #6	$162.91	13.666%	$185.1733	$185.17	$185.15	$185.20
Purchase #7	$6.87	9.522%	$7.5242	$7.52	$7.50	$7.50
7 purchase totals =	$856.09		$953.1717	$953.15	$953.10	$953.20