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	$91.85	8.568%	$99.7197	$99.72	$99.70	$99.70
Purchase #2	$192.59	13.874%	$219.3099	$219.31	$219.30	$219.30
Purchase #3	$202.74	8.854%	$220.6906	$220.69	$220.70	$220.70
Purchase #4	$213.87	13.300%	$242.3147	$242.31	$242.30	$242.30
Purchase #5	$73.76	13.497%	$83.7154	$83.72	$83.70	$83.70
Purchase #6	$79.45	7.329%	$85.2729	$85.27	$85.25	$85.30
Purchase #7	$33.46	10.606%	$37.0088	$37.01	$37.00	$37.00
7 purchase totals =	$887.72		$988.0320	$988.03	$987.95	$988.00