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	$139.30	8.563%	$151.2283	$151.23	$151.25	$151.20
Purchase #2	$120.89	7.440%	$129.8842	$129.88	$129.90	$129.90
Purchase #3	$218.61	13.515%	$248.1551	$248.16	$248.15	$248.20
Purchase #4	$199.84	7.614%	$215.0558	$215.06	$215.05	$215.10
Purchase #5	$62.58	7.798%	$67.46	$67.46	$67.45	$67.50
Purchase #6	$182.37	12.498%	$205.1626	$205.16	$205.15	$205.20
Purchase #7	$117.51	6.692%	$125.3738	$125.37	$125.35	$125.40
7 purchase totals =	$1,041.10		$1,142.3198	$1,142.32	$1,142.30	$1,142.50