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	$98.46	11.300%	$109.586	$109.59	$109.60	$109.60
Purchase #2	$232.55	3.180%	$239.9451	$239.95	$239.95	$239.90
Purchase #3	$116.41	6.792%	$124.3166	$124.32	$124.30	$124.30
Purchase #4	$70.39	3.559%	$72.8952	$72.90	$72.90	$72.90
Purchase #5	$89.26	10.635%	$98.7528	$98.75	$98.75	$98.80
Purchase #6	$225.69	6.751%	$240.9263	$240.93	$240.95	$240.90
Purchase #7	$155.55	8.260%	$168.3984	$168.40	$168.40	$168.40
7 purchase totals =	$988.31		$1,054.8204	$1,054.84	$1,054.85	$1,054.80