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	$73.28	7.707%	$78.9277	$78.93	$78.95	$78.90
Purchase #2	$198.91	8.116%	$215.0535	$215.05	$215.05	$215.10
Purchase #3	$215.47	6.429%	$229.3226	$229.32	$229.30	$229.30
Purchase #4	$13.84	3.800%	$14.3659	$14.37	$14.35	$14.40
Purchase #5	$167.58	7.362%	$179.9172	$179.92	$179.90	$179.90
Purchase #6	$155.42	4.541%	$162.4776	$162.48	$162.50	$162.50
Purchase #7	$232.96	7.530%	$250.5019	$250.50	$250.50	$250.50
7 purchase totals =	$1,057.46		$1,130.5664	$1,130.57	$1,130.55	$1,130.60