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	$203.91	3.593%	$211.2365	$211.24	$211.25	$211.20
Purchase #2	$72.86	8.269%	$78.8848	$78.88	$78.90	$78.90
Purchase #3	$52.81	12.305%	$59.3083	$59.31	$59.30	$59.30
Purchase #4	$48.84	8.105%	$52.7985	$52.80	$52.80	$52.80
Purchase #5	$164.69	10.288%	$181.6333	$181.63	$181.65	$181.60
Purchase #6	$230.92	5.517%	$243.6599	$243.66	$243.65	$243.70
Purchase #7	$159.28	9.661%	$174.668	$174.67	$174.65	$174.70
7 purchase totals =	$933.31		$1,002.1893	$1,002.19	$1,002.20	$1,002.20