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	$98.37	10.475%	$108.6743	$108.67	$108.65	$108.70
Purchase #2	$134.25	8.427%	$145.5632	$145.56	$145.55	$145.60
Purchase #3	$139.56	5.754%	$147.5903	$147.59	$147.60	$147.60
Purchase #4	$181.92	7.772%	$196.0588	$196.06	$196.05	$196.10
Purchase #5	$194.36	3.740%	$201.6291	$201.63	$201.65	$201.60
Purchase #6	$72.58	8.139%	$78.4873	$78.49	$78.50	$78.50
Purchase #7	$233.69	8.798%	$254.25	$254.25	$254.25	$254.30
7 purchase totals =	$1,054.73		$1,132.2530	$1,132.25	$1,132.25	$1,132.40