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	$13.44	6.213%	$14.275	$14.28	$14.30	$14.30
Purchase #2	$94.65	6.259%	$100.5741	$100.57	$100.55	$100.60
Purchase #3	$30.77	6.661%	$32.8196	$32.82	$32.80	$32.80
Purchase #4	$94.99	7.650%	$102.2567	$102.26	$102.25	$102.30
Purchase #5	$58.57	5.644%	$61.8757	$61.88	$61.90	$61.90
Purchase #6	$98.33	11.355%	$109.4954	$109.50	$109.50	$109.50
Purchase #7	$166.38	9.162%	$181.6237	$181.62	$181.60	$181.60
7 purchase totals =	$557.13		$602.9202	$602.93	$602.90	$603.00