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	$215.90	3.336%	$223.1024	$223.10	$223.10	$223.10
Purchase #2	$247.89	4.329%	$258.6212	$258.62	$258.60	$258.60
Purchase #3	$174.80	3.212%	$180.4146	$180.41	$180.40	$180.40
Purchase #4	$175.37	5.850%	$185.6291	$185.63	$185.65	$185.60
Purchase #5	$67.27	6.853%	$71.88	$71.88	$71.90	$71.90
Purchase #6	$133.61	6.835%	$142.7422	$142.74	$142.75	$142.70
Purchase #7	$145.27	11.680%	$162.2375	$162.24	$162.25	$162.20
7 purchase totals =	$1,160.11		$1,224.6270	$1,224.62	$1,224.65	$1,224.50