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	$62.26	8.631%	$67.6337	$67.63	$67.65	$67.60
Purchase #2	$81.27	9.282%	$88.8135	$88.81	$88.80	$88.80
Purchase #3	$161.59	12.214%	$181.3266	$181.33	$181.35	$181.30
Purchase #4	$155.83	9.855%	$171.187	$171.19	$171.20	$171.20
Purchase #5	$86.27	5.807%	$91.2797	$91.28	$91.30	$91.30
Purchase #6	$218.87	6.618%	$233.3548	$233.35	$233.35	$233.40
Purchase #7	$35.98	3.500%	$37.2393	$37.24	$37.25	$37.20
7 purchase totals =	$802.07		$870.8346	$870.83	$870.90	$870.80