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	$135.34	7.829%	$145.9358	$145.94	$145.95	$145.90
Purchase #2	$225.58	10.870%	$250.1005	$250.10	$250.10	$250.10
Purchase #3	$194.73	13.721%	$221.4489	$221.45	$221.45	$221.40
Purchase #4	$162.60	3.308%	$167.9788	$167.98	$168.00	$168.00
Purchase #5	$89.49	9.358%	$97.8645	$97.86	$97.85	$97.90
Purchase #6	$174.74	10.141%	$192.4604	$192.46	$192.45	$192.50
Purchase #7	$32.86	8.623%	$35.6935	$35.69	$35.70	$35.70
7 purchase totals =	$1,015.34		$1,111.4824	$1,111.48	$1,111.50	$1,111.50