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	$223.86	6.371%	$238.1221	$238.12	$238.10	$238.10
Purchase #2	$229.45	4.696%	$240.225	$240.23	$240.25	$240.20
Purchase #3	$146.25	6.183%	$155.2926	$155.29	$155.30	$155.30
Purchase #4	$116.28	11.678%	$129.8592	$129.86	$129.85	$129.90
Purchase #5	$56.63	12.737%	$63.843	$63.84	$63.85	$63.80
Purchase #6	$148.39	12.159%	$166.4327	$166.43	$166.45	$166.40
Purchase #7	$61.82	9.220%	$67.5198	$67.52	$67.50	$67.50
7 purchase totals =	$982.68		$1,061.2944	$1,061.29	$1,061.30	$1,061.20