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	$69.58	5.690%	$73.5391	$73.54	$73.55	$73.50
Purchase #2	$228.45	4.539%	$238.8193	$238.82	$238.80	$238.80
Purchase #3	$90.57	5.269%	$95.3421	$95.34	$95.35	$95.30
Purchase #4	$166.73	4.830%	$174.7831	$174.78	$174.80	$174.80
Purchase #5	$79.40	6.867%	$84.8524	$84.85	$84.85	$84.90
Purchase #6	$168.57	7.601%	$181.383	$181.38	$181.40	$181.40
Purchase #7	$199.31	3.410%	$206.1065	$206.11	$206.10	$206.10
7 purchase totals =	$1,002.61		$1,054.8255	$1,054.82	$1,054.85	$1,054.80