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	$215.39	13.499%	$244.4655	$244.47	$244.45	$244.50
Purchase #2	$95.80	7.489%	$102.9745	$102.97	$102.95	$103.00
Purchase #3	$170.28	9.648%	$186.7086	$186.71	$186.70	$186.70
Purchase #4	$162.37	11.640%	$181.2699	$181.27	$181.25	$181.30
Purchase #5	$144.26	8.307%	$156.2437	$156.24	$156.25	$156.20
Purchase #6	$62.49	4.499%	$65.3014	$65.30	$65.30	$65.30
Purchase #7	$77.26	7.294%	$82.8953	$82.90	$82.90	$82.90
7 purchase totals =	$927.85		$1,019.8589	$1,019.86	$1,019.80	$1,019.90