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	$49.61	5.440%	$52.3088	$52.31	$52.30	$52.30
Purchase #2	$96.56	5.750%	$102.1122	$102.11	$102.10	$102.10
Purchase #3	$248.26	5.656%	$262.3016	$262.30	$262.30	$262.30
Purchase #4	$73.68	3.776%	$76.4622	$76.46	$76.45	$76.50
Purchase #5	$78.42	5.562%	$82.7817	$82.78	$82.80	$82.80
Purchase #6	$136.89	12.671%	$154.2353	$154.24	$154.25	$154.20
Purchase #7	$54.55	8.715%	$59.304	$59.30	$59.30	$59.30
7 purchase totals =	$737.97		$789.5058	$789.50	$789.50	$789.50