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	$147.61	7.601%	$158.8298	$158.83	$158.85	$158.80
Purchase #2	$81.25	13.670%	$92.3569	$92.36	$92.35	$92.40
Purchase #3	$229.32	5.725%	$242.4486	$242.45	$242.45	$242.40
Purchase #4	$156.32	9.663%	$171.4252	$171.43	$171.45	$171.40
Purchase #5	$180.43	9.725%	$197.9768	$197.98	$198.00	$198.00
Purchase #6	$25.35	7.690%	$27.2994	$27.30	$27.30	$27.30
Purchase #7	$106.87	5.426%	$112.6688	$112.67	$112.65	$112.70
7 purchase totals =	$927.15		$1,003.0055	$1,003.02	$1,003.05	$1,003.00