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	$238.94	10.758%	$264.6452	$264.65	$264.65	$264.60
Purchase #2	$183.37	9.483%	$200.759	$200.76	$200.75	$200.80
Purchase #3	$26.43	5.599%	$27.9098	$27.91	$27.90	$27.90
Purchase #4	$36.77	13.213%	$41.6284	$41.63	$41.65	$41.60
Purchase #5	$181.88	5.860%	$192.5382	$192.54	$192.55	$192.50
Purchase #6	$158.71	4.700%	$166.1694	$166.17	$166.15	$166.20
Purchase #7	$54.99	8.131%	$59.4612	$59.46	$59.45	$59.50
7 purchase totals =	$881.09		$953.1112	$953.12	$953.10	$953.10