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	$248.86	5.346%	$262.1641	$262.16	$262.15	$262.20
Purchase #2	$51.53	13.215%	$58.3397	$58.34	$58.35	$58.30
Purchase #3	$170.85	4.571%	$178.6596	$178.66	$178.65	$178.70
Purchase #4	$203.50	9.266%	$222.3563	$222.36	$222.35	$222.40
Purchase #5	$74.91	4.255%	$78.0974	$78.10	$78.10	$78.10
Purchase #6	$85.33	5.299%	$89.8516	$89.85	$89.85	$89.90
Purchase #7	$145.87	9.218%	$159.3163	$159.32	$159.30	$159.30
7 purchase totals =	$980.85		$1,048.7850	$1,048.79	$1,048.75	$1,048.90