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	$52.73	7.644%	$56.7607	$56.76	$56.75	$56.80
Purchase #2	$174.69	13.610%	$198.4653	$198.47	$198.45	$198.50
Purchase #3	$67.65	7.747%	$72.8908	$72.89	$72.90	$72.90
Purchase #4	$170.42	12.164%	$191.1499	$191.15	$191.15	$191.10
Purchase #5	$186.90	4.784%	$195.8413	$195.84	$195.85	$195.80
Purchase #6	$226.27	4.813%	$237.1604	$237.16	$237.15	$237.20
Purchase #7	$250.86	3.273%	$259.0706	$259.07	$259.05	$259.10
7 purchase totals =	$1,129.52		$1,211.3390	$1,211.34	$1,211.30	$1,211.40