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	$51.48	7.775%	$55.4826	$55.48	$55.50	$55.50
Purchase #2	$134.41	12.791%	$151.6024	$151.60	$151.60	$151.60
Purchase #3	$98.27	8.416%	$106.5404	$106.54	$106.55	$106.50
Purchase #4	$142.80	9.498%	$156.3631	$156.36	$156.35	$156.40
Purchase #5	$52.58	3.669%	$54.5092	$54.51	$54.50	$54.50
Purchase #6	$56.56	11.214%	$62.9026	$62.90	$62.90	$62.90
Purchase #7	$245.86	8.257%	$266.1607	$266.16	$266.15	$266.20
7 purchase totals =	$781.96		$853.5610	$853.55	$853.55	$853.60