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	$94.31	13.742%	$107.2701	$107.27	$107.25	$107.30
Purchase #2	$49.92	3.201%	$51.5179	$51.52	$51.50	$51.50
Purchase #3	$35.52	5.419%	$37.4448	$37.44	$37.45	$37.40
Purchase #4	$72.73	13.209%	$82.3369	$82.34	$82.35	$82.30
Purchase #5	$195.36	8.118%	$211.2193	$211.22	$211.20	$211.20
Purchase #6	$39.56	5.501%	$41.7362	$41.74	$41.75	$41.70
Purchase #7	$25.76	13.848%	$29.3272	$29.33	$29.35	$29.30
7 purchase totals =	$513.16		$560.8524	$560.86	$560.85	$560.70