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	$36.91	3.618%	$38.2454	$38.25	$38.25	$38.20
Purchase #2	$57.31	4.495%	$59.8861	$59.89	$59.90	$59.90
Purchase #3	$184.91	5.290%	$194.6917	$194.69	$194.70	$194.70
Purchase #4	$172.86	12.592%	$194.6265	$194.63	$194.65	$194.60
Purchase #5	$194.76	12.820%	$219.7282	$219.73	$219.75	$219.70
Purchase #6	$5.34	3.345%	$5.5186	$5.52	$5.50	$5.50
Purchase #7	$73.58	12.158%	$82.5259	$82.53	$82.55	$82.50
7 purchase totals =	$725.67		$795.2224	$795.24	$795.30	$795.10