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	$127.91	10.308%	$141.095	$141.10	$141.10	$141.10
Purchase #2	$105.61	3.227%	$109.018	$109.02	$109.00	$109.00
Purchase #3	$186.89	7.221%	$200.3853	$200.39	$200.40	$200.40
Purchase #4	$204.30	6.257%	$217.0831	$217.08	$217.10	$217.10
Purchase #5	$37.84	9.612%	$41.4772	$41.48	$41.50	$41.50
Purchase #6	$183.77	3.147%	$189.5532	$189.55	$189.55	$189.60
Purchase #7	$245.98	3.300%	$254.0973	$254.10	$254.10	$254.10
7 purchase totals =	$1,092.30		$1,152.7091	$1,152.72	$1,152.75	$1,152.80