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	$81.59	12.662%	$91.9209	$91.92	$91.90	$91.90
Purchase #2	$219.25	13.629%	$249.1316	$249.13	$249.15	$249.10
Purchase #3	$165.27	6.336%	$175.7415	$175.74	$175.75	$175.70
Purchase #4	$171.84	5.634%	$181.5215	$181.52	$181.50	$181.50
Purchase #5	$91.83	12.585%	$103.3868	$103.39	$103.40	$103.40
Purchase #6	$236.98	12.561%	$266.7471	$266.75	$266.75	$266.70
Purchase #7	$29.39	9.248%	$32.108	$32.11	$32.10	$32.10
7 purchase totals =	$996.15		$1,100.5574	$1,100.56	$1,100.55	$1,100.40