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	$42.51	11.192%	$47.2677	$47.27	$47.25	$47.30
Purchase #2	$81.47	9.602%	$89.2927	$89.29	$89.30	$89.30
Purchase #3	$84.46	9.272%	$92.2911	$92.29	$92.30	$92.30
Purchase #4	$242.41	12.552%	$272.8373	$272.84	$272.85	$272.80
Purchase #5	$86.26	5.342%	$90.868	$90.87	$90.85	$90.90
Purchase #6	$160.99	13.596%	$182.8782	$182.88	$182.90	$182.90
Purchase #7	$155.41	8.685%	$168.9074	$168.91	$168.90	$168.90
7 purchase totals =	$853.51		$944.3424	$944.35	$944.35	$944.40