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	$102.95	4.254%	$107.3295	$107.33	$107.35	$107.30
Purchase #2	$108.86	5.424%	$114.7646	$114.76	$114.75	$114.80
Purchase #3	$61.50	10.456%	$67.9304	$67.93	$67.95	$67.90
Purchase #4	$59.34	4.529%	$62.0275	$62.03	$62.05	$62.00
Purchase #5	$154.85	3.768%	$160.6847	$160.68	$160.70	$160.70
Purchase #6	$177.25	10.800%	$196.393	$196.39	$196.40	$196.40
Purchase #7	$37.79	6.736%	$40.3355	$40.34	$40.35	$40.30
7 purchase totals =	$702.54		$749.4652	$749.46	$749.55	$749.40