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	$130.97	6.263%	$139.1727	$139.17	$139.15	$139.20
Purchase #2	$171.33	6.354%	$182.2163	$182.22	$182.20	$182.20
Purchase #3	$233.67	5.132%	$245.6619	$245.66	$245.65	$245.70
Purchase #4	$98.51	11.451%	$109.7904	$109.79	$109.80	$109.80
Purchase #5	$93.81	8.185%	$101.4883	$101.49	$101.50	$101.50
Purchase #6	$237.45	8.798%	$258.3409	$258.34	$258.35	$258.30
Purchase #7	$23.63	6.164%	$25.0866	$25.09	$25.10	$25.10
7 purchase totals =	$989.37		$1,061.7571	$1,061.76	$1,061.75	$1,061.80