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	$159.92	8.650%	$173.7531	$173.75	$173.75	$173.80
Purchase #2	$46.78	10.462%	$51.6741	$51.67	$51.65	$51.70
Purchase #3	$85.98	9.123%	$93.824	$93.82	$93.80	$93.80
Purchase #4	$36.56	10.346%	$40.3425	$40.34	$40.35	$40.30
Purchase #5	$218.64	10.811%	$242.2772	$242.28	$242.30	$242.30
Purchase #6	$42.49	7.133%	$45.5208	$45.52	$45.50	$45.50
Purchase #7	$42.45	9.494%	$46.4802	$46.48	$46.50	$46.50
7 purchase totals =	$632.82		$693.8719	$693.86	$693.85	$693.90