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	$246.94	6.703%	$263.4924	$263.49	$263.50	$263.50
Purchase #2	$149.72	4.363%	$156.2523	$156.25	$156.25	$156.30
Purchase #3	$170.59	11.463%	$190.1447	$190.14	$190.15	$190.10
Purchase #4	$74.91	11.216%	$83.3119	$83.31	$83.30	$83.30
Purchase #5	$121.59	12.316%	$136.565	$136.57	$136.55	$136.60
Purchase #6	$106.80	7.122%	$114.4063	$114.41	$114.40	$114.40
Purchase #7	$196.96	4.622%	$206.0635	$206.06	$206.05	$206.10
7 purchase totals =	$1,067.51		$1,150.2361	$1,150.23	$1,150.20	$1,150.30