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	$136.27	3.814%	$141.4673	$141.47	$141.45	$141.50
Purchase #2	$51.83	10.794%	$57.4245	$57.42	$57.40	$57.40
Purchase #3	$98.56	7.696%	$106.1452	$106.15	$106.15	$106.10
Purchase #4	$237.92	7.790%	$256.454	$256.45	$256.45	$256.50
Purchase #5	$150.85	12.454%	$169.6369	$169.64	$169.65	$169.60
Purchase #6	$182.61	5.311%	$192.3084	$192.31	$192.30	$192.30
Purchase #7	$159.69	5.754%	$168.8786	$168.88	$168.90	$168.90
7 purchase totals =	$1,017.73		$1,092.3149	$1,092.32	$1,092.30	$1,092.30