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	$103.53	4.116%	$107.7913	$107.79	$107.80	$107.80
Purchase #2	$171.89	3.740%	$178.3187	$178.32	$178.30	$178.30
Purchase #3	$64.41	8.637%	$69.9731	$69.97	$69.95	$70.00
Purchase #4	$134.37	6.359%	$142.9146	$142.91	$142.90	$142.90
Purchase #5	$137.27	9.383%	$150.15	$150.15	$150.15	$150.20
Purchase #6	$154.39	12.412%	$173.5529	$173.55	$173.55	$173.60
Purchase #7	$169.59	6.274%	$180.2301	$180.23	$180.25	$180.20
7 purchase totals =	$935.45		$1,002.9307	$1,002.92	$1,002.90	$1,003.00