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	$178.36	10.118%	$196.4065	$196.41	$196.40	$196.40
Purchase #2	$19.83	4.159%	$20.6547	$20.65	$20.65	$20.70
Purchase #3	$69.78	12.779%	$78.6972	$78.70	$78.70	$78.70
Purchase #4	$161.89	9.581%	$177.4007	$177.40	$177.40	$177.40
Purchase #5	$98.33	7.223%	$105.4324	$105.43	$105.45	$105.40
Purchase #6	$82.89	8.765%	$90.1553	$90.16	$90.15	$90.20
Purchase #7	$96.61	8.732%	$105.046	$105.05	$105.05	$105.00
7 purchase totals =	$707.69		$773.7928	$773.80	$773.80	$773.80