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	$77.33	6.760%	$82.5575	$82.56	$82.55	$82.60
Purchase #2	$208.65	3.550%	$216.0571	$216.06	$216.05	$216.10
Purchase #3	$184.44	5.675%	$194.907	$194.91	$194.90	$194.90
Purchase #4	$99.63	3.719%	$103.3352	$103.34	$103.35	$103.30
Purchase #5	$230.63	3.506%	$238.7159	$238.72	$238.70	$238.70
Purchase #6	$93.51	13.686%	$106.3078	$106.31	$106.30	$106.30
Purchase #7	$139.46	3.730%	$144.6619	$144.66	$144.65	$144.70
7 purchase totals =	$1,033.65		$1,086.5424	$1,086.56	$1,086.50	$1,086.60