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	$58.66	5.768%	$62.0435	$62.04	$62.05	$62.00
Purchase #2	$219.30	6.334%	$233.1905	$233.19	$233.20	$233.20
Purchase #3	$109.66	7.132%	$117.481	$117.48	$117.50	$117.50
Purchase #4	$6.88	4.359%	$7.1799	$7.18	$7.20	$7.20
Purchase #5	$68.35	6.445%	$72.7552	$72.76	$72.75	$72.80
Purchase #6	$96.56	11.248%	$107.4211	$107.42	$107.40	$107.40
Purchase #7	$61.35	8.209%	$66.3862	$66.39	$66.40	$66.40
7 purchase totals =	$620.76		$666.4574	$666.46	$666.50	$666.50