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	$71.38	10.608%	$78.952	$78.95	$78.95	$79.00
Purchase #2	$31.26	3.449%	$32.3382	$32.34	$32.35	$32.30
Purchase #3	$180.74	4.861%	$189.5258	$189.53	$189.55	$189.50
Purchase #4	$149.96	11.710%	$167.5203	$167.52	$167.50	$167.50
Purchase #5	$141.36	11.326%	$157.3704	$157.37	$157.35	$157.40
Purchase #6	$176.61	7.812%	$190.4068	$190.41	$190.40	$190.40
Purchase #7	$120.61	6.398%	$128.3266	$128.33	$128.35	$128.30
7 purchase totals =	$871.92		$944.4401	$944.45	$944.45	$944.40