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	$80.34	3.127%	$82.8522	$82.85	$82.85	$82.90
Purchase #2	$162.73	12.154%	$182.5082	$182.51	$182.50	$182.50
Purchase #3	$91.38	5.633%	$96.5274	$96.53	$96.55	$96.50
Purchase #4	$199.78	8.523%	$216.8072	$216.81	$216.80	$216.80
Purchase #5	$156.26	8.140%	$168.9796	$168.98	$169.00	$169.00
Purchase #6	$165.87	11.718%	$185.3066	$185.31	$185.30	$185.30
Purchase #7	$188.29	3.727%	$195.3076	$195.31	$195.30	$195.30
7 purchase totals =	$1,044.65		$1,128.2888	$1,128.30	$1,128.30	$1,128.30