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	$50.28	5.263%	$52.9262	$52.93	$52.95	$52.90
Purchase #2	$249.52	12.555%	$280.8472	$280.85	$280.85	$280.80
Purchase #3	$42.46	3.263%	$43.8455	$43.85	$43.85	$43.80
Purchase #4	$147.85	11.129%	$164.3042	$164.30	$164.30	$164.30
Purchase #5	$239.55	4.608%	$250.5885	$250.59	$250.60	$250.60
Purchase #6	$216.63	5.859%	$229.3224	$229.32	$229.30	$229.30
Purchase #7	$98.50	5.148%	$103.5708	$103.57	$103.55	$103.60
7 purchase totals =	$1,044.79		$1,125.4048	$1,125.41	$1,125.40	$1,125.30