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	$50.83	5.759%	$53.7573	$53.76	$53.75	$53.80
Purchase #2	$25.72	9.792%	$28.2385	$28.24	$28.25	$28.20
Purchase #3	$232.42	13.851%	$264.6125	$264.61	$264.60	$264.60
Purchase #4	$145.61	5.230%	$153.2254	$153.23	$153.25	$153.20
Purchase #5	$250.76	8.216%	$271.3624	$271.36	$271.35	$271.40
Purchase #6	$185.56	6.466%	$197.5583	$197.56	$197.55	$197.60
Purchase #7	$45.53	4.418%	$47.5415	$47.54	$47.55	$47.50
7 purchase totals =	$936.43		$1,016.2959	$1,016.30	$1,016.30	$1,016.30