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	$24.72	4.449%	$25.8198	$25.82	$25.80	$25.80
Purchase #2	$178.67	5.512%	$188.5183	$188.52	$188.50	$188.50
Purchase #3	$232.50	13.805%	$264.5966	$264.60	$264.60	$264.60
Purchase #4	$174.56	6.806%	$186.4406	$186.44	$186.45	$186.40
Purchase #5	$216.48	10.158%	$238.47	$238.47	$238.45	$238.50
Purchase #6	$240.58	11.614%	$268.521	$268.52	$268.50	$268.50
Purchase #7	$117.97	10.737%	$130.6364	$130.64	$130.65	$130.60
7 purchase totals =	$1,185.48		$1,303.0027	$1,303.01	$1,302.95	$1,302.90