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	$156.37	9.126%	$170.6403	$170.64	$170.65	$170.60
Purchase #2	$138.41	3.254%	$142.9139	$142.91	$142.90	$142.90
Purchase #3	$27.59	4.459%	$28.8202	$28.82	$28.80	$28.80
Purchase #4	$89.60	7.309%	$96.1489	$96.15	$96.15	$96.10
Purchase #5	$35.74	8.189%	$38.6667	$38.67	$38.65	$38.70
Purchase #6	$33.92	5.816%	$35.8928	$35.89	$35.90	$35.90
Purchase #7	$184.70	3.540%	$191.2384	$191.24	$191.25	$191.20
7 purchase totals =	$666.33		$704.3212	$704.32	$704.30	$704.20