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	$33.94	9.177%	$37.0547	$37.05	$37.05	$37.10
Purchase #2	$91.89	9.208%	$100.3512	$100.35	$100.35	$100.40
Purchase #3	$166.98	12.459%	$187.784	$187.78	$187.80	$187.80
Purchase #4	$108.55	10.600%	$120.0563	$120.06	$120.05	$120.10
Purchase #5	$185.92	11.224%	$206.7877	$206.79	$206.80	$206.80
Purchase #6	$246.85	12.134%	$276.8028	$276.80	$276.80	$276.80
Purchase #7	$181.44	3.554%	$187.8884	$187.89	$187.90	$187.90
7 purchase totals =	$1,015.57		$1,116.7251	$1,116.72	$1,116.75	$1,116.90