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	$104.25	7.466%	$112.0333	$112.03	$112.05	$112.00
Purchase #2	$250.72	5.330%	$264.0834	$264.08	$264.10	$264.10
Purchase #3	$92.75	6.241%	$98.5385	$98.54	$98.55	$98.50
Purchase #4	$78.84	3.676%	$81.7382	$81.74	$81.75	$81.70
Purchase #5	$87.74	3.121%	$90.4784	$90.48	$90.50	$90.50
Purchase #6	$224.96	8.424%	$243.9106	$243.91	$243.90	$243.90
Purchase #7	$169.55	4.585%	$177.3239	$177.32	$177.30	$177.30
7 purchase totals =	$1,008.81		$1,068.1063	$1,068.10	$1,068.15	$1,068.00