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	$204.67	11.531%	$228.2705	$228.27	$228.25	$228.30
Purchase #2	$186.53	4.309%	$194.5676	$194.57	$194.55	$194.60
Purchase #3	$36.56	11.411%	$40.7319	$40.73	$40.75	$40.70
Purchase #4	$64.97	11.221%	$72.2603	$72.26	$72.25	$72.30
Purchase #5	$46.50	13.609%	$52.8282	$52.83	$52.85	$52.80
Purchase #6	$173.44	12.148%	$194.5095	$194.51	$194.50	$194.50
Purchase #7	$88.26	9.777%	$96.8892	$96.89	$96.90	$96.90
7 purchase totals =	$800.93		$880.0572	$880.06	$880.05	$880.10