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	$171.98	7.867%	$185.5097	$185.51	$185.50	$185.50
Purchase #2	$113.75	9.691%	$124.7735	$124.77	$124.75	$124.80
Purchase #3	$166.68	5.510%	$175.8641	$175.86	$175.85	$175.90
Purchase #4	$120.36	9.280%	$131.5294	$131.53	$131.55	$131.50
Purchase #5	$70.30	3.236%	$72.5749	$72.57	$72.55	$72.60
Purchase #6	$132.54	12.853%	$149.5754	$149.58	$149.60	$149.60
Purchase #7	$180.73	13.221%	$204.6243	$204.62	$204.60	$204.60
7 purchase totals =	$956.34		$1,044.4513	$1,044.44	$1,044.40	$1,044.50