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	$94.79	3.801%	$98.393	$98.39	$98.40	$98.40
Purchase #2	$245.40	9.565%	$268.8725	$268.87	$268.85	$268.90
Purchase #3	$192.45	10.728%	$213.096	$213.10	$213.10	$213.10
Purchase #4	$28.98	5.229%	$30.4954	$30.50	$30.50	$30.50
Purchase #5	$221.54	3.623%	$229.5664	$229.57	$229.55	$229.60
Purchase #6	$242.83	11.744%	$271.348	$271.35	$271.35	$271.30
Purchase #7	$57.78	3.730%	$59.9352	$59.94	$59.95	$59.90
7 purchase totals =	$1,083.77		$1,171.7065	$1,171.72	$1,171.70	$1,171.70