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	$174.60	3.414%	$180.5608	$180.56	$180.55	$180.60
Purchase #2	$247.77	10.366%	$273.4538	$273.45	$273.45	$273.50
Purchase #3	$142.53	6.543%	$151.8557	$151.86	$151.85	$151.90
Purchase #4	$44.97	3.685%	$46.6271	$46.63	$46.65	$46.60
Purchase #5	$167.72	11.448%	$186.9206	$186.92	$186.90	$186.90
Purchase #6	$176.35	7.343%	$189.2994	$189.30	$189.30	$189.30
Purchase #7	$77.88	4.594%	$81.4578	$81.46	$81.45	$81.50
7 purchase totals =	$1,031.82		$1,110.1752	$1,110.18	$1,110.15	$1,110.30