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	$174.57	12.339%	$196.1102	$196.11	$196.10	$196.10
Purchase #2	$209.35	12.418%	$235.3471	$235.35	$235.35	$235.30
Purchase #3	$83.83	10.680%	$92.783	$92.78	$92.80	$92.80
Purchase #4	$158.84	4.782%	$166.4357	$166.44	$166.45	$166.40
Purchase #5	$26.53	4.716%	$27.7812	$27.78	$27.80	$27.80
Purchase #6	$29.78	4.696%	$31.1785	$31.18	$31.20	$31.20
Purchase #7	$75.80	3.793%	$78.6751	$78.68	$78.70	$78.70
7 purchase totals =	$758.70		$828.3108	$828.32	$828.40	$828.30