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	$167.74	3.751%	$174.0319	$174.03	$174.05	$174.00
Purchase #2	$101.83	7.642%	$109.6118	$109.61	$109.60	$109.60
Purchase #3	$201.72	12.823%	$227.5866	$227.59	$227.60	$227.60
Purchase #4	$60.67	11.288%	$67.5184	$67.52	$67.50	$67.50
Purchase #5	$88.77	10.120%	$97.7535	$97.75	$97.75	$97.80
Purchase #6	$35.54	6.518%	$37.8565	$37.86	$37.85	$37.90
Purchase #7	$113.27	4.579%	$118.4566	$118.46	$118.45	$118.50
7 purchase totals =	$769.54		$832.8153	$832.82	$832.80	$832.90