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	$168.67	5.616%	$178.1425	$178.14	$178.15	$178.10
Purchase #2	$68.35	10.184%	$75.3108	$75.31	$75.30	$75.30
Purchase #3	$73.32	6.577%	$78.1423	$78.14	$78.15	$78.10
Purchase #4	$209.54	13.603%	$238.0437	$238.04	$238.05	$238.00
Purchase #5	$185.90	13.460%	$210.9221	$210.92	$210.90	$210.90
Purchase #6	$207.66	5.134%	$218.3213	$218.32	$218.30	$218.30
Purchase #7	$81.37	6.376%	$86.5582	$86.56	$86.55	$86.60
7 purchase totals =	$994.81		$1,085.4409	$1,085.43	$1,085.40	$1,085.30