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	$104.87	5.250%	$110.3757	$110.38	$110.40	$110.40
Purchase #2	$205.58	12.332%	$230.9321	$230.93	$230.95	$230.90
Purchase #3	$231.93	7.557%	$249.457	$249.46	$249.45	$249.50
Purchase #4	$14.42	4.681%	$15.095	$15.10	$15.10	$15.10
Purchase #5	$104.41	4.769%	$109.3893	$109.39	$109.40	$109.40
Purchase #6	$178.83	4.314%	$186.5447	$186.54	$186.55	$186.50
Purchase #7	$36.49	10.251%	$40.2306	$40.23	$40.25	$40.20
7 purchase totals =	$876.53		$942.0244	$942.03	$942.10	$942.00