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	$61.50	9.457%	$67.3161	$67.32	$67.30	$67.30
Purchase #2	$218.33	3.655%	$226.31	$226.31	$226.30	$226.30
Purchase #3	$109.83	7.337%	$117.8882	$117.89	$117.90	$117.90
Purchase #4	$79.31	9.251%	$86.647	$86.65	$86.65	$86.60
Purchase #5	$142.68	8.111%	$154.2528	$154.25	$154.25	$154.30
Purchase #6	$117.27	8.302%	$127.0058	$127.01	$127.00	$127.00
Purchase #7	$136.76	4.809%	$143.3368	$143.34	$143.35	$143.30
7 purchase totals =	$865.68		$922.7567	$922.77	$922.75	$922.70