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	$147.32	11.705%	$164.5638	$164.56	$164.55	$164.60
Purchase #2	$36.51	12.437%	$41.0507	$41.05	$41.05	$41.10
Purchase #3	$85.41	4.874%	$89.5729	$89.57	$89.55	$89.60
Purchase #4	$243.29	13.539%	$276.229	$276.23	$276.25	$276.20
Purchase #5	$228.92	7.419%	$245.9036	$245.90	$245.90	$245.90
Purchase #6	$49.71	13.520%	$56.4308	$56.43	$56.45	$56.40
Purchase #7	$218.60	5.262%	$230.1027	$230.10	$230.10	$230.10
7 purchase totals =	$1,009.76		$1,103.8535	$1,103.84	$1,103.85	$1,103.90