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	$189.66	3.792%	$196.8519	$196.85	$196.85	$196.90
Purchase #2	$104.56	8.635%	$113.5888	$113.59	$113.60	$113.60
Purchase #3	$41.41	4.556%	$43.2966	$43.30	$43.30	$43.30
Purchase #4	$243.39	4.630%	$254.659	$254.66	$254.65	$254.70
Purchase #5	$91.71	8.345%	$99.3632	$99.36	$99.35	$99.40
Purchase #6	$26.92	6.553%	$28.6841	$28.68	$28.70	$28.70
Purchase #7	$232.28	3.596%	$240.6328	$240.63	$240.65	$240.60
7 purchase totals =	$929.93		$977.0764	$977.07	$977.10	$977.20