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	$69.60	12.564%	$78.3445	$78.34	$78.35	$78.30
Purchase #2	$188.98	9.682%	$207.277	$207.28	$207.30	$207.30
Purchase #3	$242.63	8.151%	$262.4068	$262.41	$262.40	$262.40
Purchase #4	$226.44	12.487%	$254.7156	$254.72	$254.70	$254.70
Purchase #5	$97.96	3.359%	$101.2505	$101.25	$101.25	$101.30
Purchase #6	$131.29	12.614%	$147.8509	$147.85	$147.85	$147.90
Purchase #7	$39.82	10.194%	$43.8793	$43.88	$43.90	$43.90
7 purchase totals =	$996.72		$1,095.7246	$1,095.73	$1,095.75	$1,095.80