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	$206.72	5.468%	$218.0234	$218.02	$218.00	$218.00
Purchase #2	$86.37	3.751%	$89.6097	$89.61	$89.60	$89.60
Purchase #3	$203.67	7.805%	$219.5664	$219.57	$219.55	$219.60
Purchase #4	$103.38	4.523%	$108.0559	$108.06	$108.05	$108.10
Purchase #5	$56.73	13.480%	$64.3772	$64.38	$64.40	$64.40
Purchase #6	$140.50	5.137%	$147.7175	$147.72	$147.70	$147.70
Purchase #7	$163.87	4.515%	$171.2687	$171.27	$171.25	$171.30
7 purchase totals =	$961.24		$1,018.6188	$1,018.63	$1,018.55	$1,018.70