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	$174.39	6.807%	$186.2607	$186.26	$186.25	$186.30
Purchase #2	$144.71	12.172%	$162.3241	$162.32	$162.30	$162.30
Purchase #3	$235.97	3.443%	$244.0944	$244.09	$244.10	$244.10
Purchase #4	$135.89	8.522%	$147.4705	$147.47	$147.45	$147.50
Purchase #5	$27.34	5.492%	$28.8415	$28.84	$28.85	$28.80
Purchase #6	$232.94	7.278%	$249.8934	$249.89	$249.90	$249.90
Purchase #7	$118.27	8.158%	$127.9185	$127.92	$127.90	$127.90
7 purchase totals =	$1,069.51		$1,146.8031	$1,146.79	$1,146.75	$1,146.80