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	$73.57	5.689%	$77.7554	$77.76	$77.75	$77.80
Purchase #2	$74.61	11.580%	$83.2498	$83.25	$83.25	$83.20
Purchase #3	$167.90	9.305%	$183.5231	$183.52	$183.50	$183.50
Purchase #4	$96.85	11.401%	$107.8919	$107.89	$107.90	$107.90
Purchase #5	$137.31	13.119%	$155.3237	$155.32	$155.30	$155.30
Purchase #6	$173.54	13.150%	$196.3605	$196.36	$196.35	$196.40
Purchase #7	$107.84	6.258%	$114.5886	$114.59	$114.60	$114.60
7 purchase totals =	$831.62		$918.6930	$918.69	$918.65	$918.70