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	$194.36	10.322%	$214.4218	$214.42	$214.40	$214.40
Purchase #2	$76.28	9.394%	$83.4457	$83.45	$83.45	$83.40
Purchase #3	$65.49	10.129%	$72.1235	$72.12	$72.10	$72.10
Purchase #4	$90.66	6.350%	$96.4169	$96.42	$96.40	$96.40
Purchase #5	$245.40	3.471%	$253.9178	$253.92	$253.90	$253.90
Purchase #6	$218.82	10.423%	$241.6276	$241.63	$241.65	$241.60
Purchase #7	$84.64	5.676%	$89.4442	$89.44	$89.45	$89.40
7 purchase totals =	$975.65		$1,051.3975	$1,051.40	$1,051.35	$1,051.20