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	$215.40	6.468%	$229.3321	$229.33	$229.35	$229.30
Purchase #2	$207.65	7.699%	$223.637	$223.64	$223.65	$223.60
Purchase #3	$8.32	12.801%	$9.385	$9.39	$9.40	$9.40
Purchase #4	$161.31	3.631%	$167.1672	$167.17	$167.15	$167.20
Purchase #5	$174.59	11.695%	$195.0083	$195.01	$195.00	$195.00
Purchase #6	$161.76	6.252%	$171.8732	$171.87	$171.85	$171.90
Purchase #7	$69.42	13.146%	$78.546	$78.55	$78.55	$78.50
7 purchase totals =	$998.45		$1,074.9488	$1,074.96	$1,074.95	$1,074.90