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	$169.80	10.163%	$187.0568	$187.06	$187.05	$187.10
Purchase #2	$220.77	12.300%	$247.9247	$247.92	$247.90	$247.90
Purchase #3	$174.90	4.360%	$182.5256	$182.53	$182.55	$182.50
Purchase #4	$36.77	5.826%	$38.9122	$38.91	$38.90	$38.90
Purchase #5	$235.26	3.488%	$243.4659	$243.47	$243.45	$243.50
Purchase #6	$55.28	10.722%	$61.2071	$61.21	$61.20	$61.20
Purchase #7	$59.32	4.109%	$61.7575	$61.76	$61.75	$61.80
7 purchase totals =	$952.10		$1,022.8498	$1,022.86	$1,022.80	$1,022.90