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	$97.51	10.551%	$107.7983	$107.80	$107.80	$107.80
Purchase #2	$245.26	7.748%	$264.2627	$264.26	$264.25	$264.30
Purchase #3	$39.40	3.579%	$40.8101	$40.81	$40.80	$40.80
Purchase #4	$170.51	10.196%	$187.8952	$187.90	$187.90	$187.90
Purchase #5	$196.82	7.448%	$211.4792	$211.48	$211.50	$211.50
Purchase #6	$146.75	3.500%	$151.8863	$151.89	$151.90	$151.90
Purchase #7	$83.35	7.543%	$89.6371	$89.64	$89.65	$89.60
7 purchase totals =	$979.60		$1,053.7689	$1,053.78	$1,053.80	$1,053.80