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	$144.27	5.780%	$152.6088	$152.61	$152.60	$152.60
Purchase #2	$91.91	12.202%	$103.1249	$103.12	$103.10	$103.10
Purchase #3	$173.37	9.353%	$189.5853	$189.59	$189.60	$189.60
Purchase #4	$201.34	8.730%	$218.917	$218.92	$218.90	$218.90
Purchase #5	$91.99	8.608%	$99.9085	$99.91	$99.90	$99.90
Purchase #6	$162.67	12.639%	$183.2299	$183.23	$183.25	$183.20
Purchase #7	$128.66	7.796%	$138.6903	$138.69	$138.70	$138.70
7 purchase totals =	$994.21		$1,086.0647	$1,086.07	$1,086.05	$1,086.00