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	$211.57	4.642%	$221.3911	$221.39	$221.40	$221.40
Purchase #2	$40.56	7.269%	$43.5083	$43.51	$43.50	$43.50
Purchase #3	$54.88	10.713%	$60.7593	$60.76	$60.75	$60.80
Purchase #4	$215.93	12.123%	$242.1072	$242.11	$242.10	$242.10
Purchase #5	$180.96	11.218%	$201.2601	$201.26	$201.25	$201.30
Purchase #6	$205.99	7.672%	$221.7936	$221.79	$221.80	$221.80
Purchase #7	$54.93	8.308%	$59.4936	$59.49	$59.50	$59.50
7 purchase totals =	$964.82		$1,050.3132	$1,050.31	$1,050.30	$1,050.40