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	$210.30	4.655%	$220.0895	$220.09	$220.10	$220.10
Purchase #2	$81.83	5.677%	$86.4755	$86.48	$86.50	$86.50
Purchase #3	$120.63	4.363%	$125.8931	$125.89	$125.90	$125.90
Purchase #4	$181.82	12.240%	$204.0748	$204.07	$204.05	$204.10
Purchase #5	$78.98	13.769%	$89.8548	$89.85	$89.85	$89.90
Purchase #6	$184.98	3.653%	$191.7373	$191.74	$191.75	$191.70
Purchase #7	$196.35	12.695%	$221.2766	$221.28	$221.30	$221.30
7 purchase totals =	$1,054.89		$1,139.4016	$1,139.40	$1,139.45	$1,139.50