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	$99.73	13.180%	$112.8744	$112.87	$112.85	$112.90
Purchase #2	$64.77	4.321%	$67.5687	$67.57	$67.55	$67.60
Purchase #3	$53.84	11.233%	$59.8878	$59.89	$59.90	$59.90
Purchase #4	$161.36	7.872%	$174.0623	$174.06	$174.05	$174.10
Purchase #5	$134.57	11.751%	$150.3833	$150.38	$150.40	$150.40
Purchase #6	$236.89	9.311%	$258.9468	$258.95	$258.95	$258.90
Purchase #7	$223.72	9.792%	$245.6267	$245.63	$245.65	$245.60
7 purchase totals =	$974.88		$1,069.3500	$1,069.35	$1,069.35	$1,069.40