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	$218.27	4.852%	$228.8605	$228.86	$228.85	$228.90
Purchase #2	$150.96	7.567%	$162.3831	$162.38	$162.40	$162.40
Purchase #3	$110.75	3.226%	$114.3228	$114.32	$114.30	$114.30
Purchase #4	$5.89	10.106%	$6.4852	$6.49	$6.50	$6.50
Purchase #5	$203.86	3.215%	$210.4141	$210.41	$210.40	$210.40
Purchase #6	$243.32	13.351%	$275.8057	$275.81	$275.80	$275.80
Purchase #7	$45.89	13.580%	$52.1219	$52.12	$52.10	$52.10
7 purchase totals =	$978.94		$1,050.3933	$1,050.39	$1,050.35	$1,050.40