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	$189.78	3.560%	$196.5362	$196.54	$196.55	$196.50
Purchase #2	$240.57	10.391%	$265.5676	$265.57	$265.55	$265.60
Purchase #3	$157.79	11.194%	$175.453	$175.45	$175.45	$175.50
Purchase #4	$186.78	4.454%	$195.0992	$195.10	$195.10	$195.10
Purchase #5	$250.71	5.243%	$263.8547	$263.85	$263.85	$263.90
Purchase #6	$161.37	4.817%	$169.1432	$169.14	$169.15	$169.10
Purchase #7	$59.54	4.267%	$62.0806	$62.08	$62.10	$62.10
7 purchase totals =	$1,246.54		$1,327.7345	$1,327.73	$1,327.75	$1,327.80