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	$238.70	4.717%	$249.9595	$249.96	$249.95	$250.00
Purchase #2	$93.46	3.573%	$96.7993	$96.80	$96.80	$96.80
Purchase #3	$160.82	12.790%	$181.3889	$181.39	$181.40	$181.40
Purchase #4	$148.30	11.529%	$165.3975	$165.40	$165.40	$165.40
Purchase #5	$28.36	4.424%	$29.6146	$29.61	$29.60	$29.60
Purchase #6	$185.90	5.671%	$196.4424	$196.44	$196.45	$196.40
Purchase #7	$244.82	3.747%	$253.9934	$253.99	$254.00	$254.00
7 purchase totals =	$1,100.36		$1,173.5956	$1,173.59	$1,173.60	$1,173.60