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	$135.48	12.320%	$152.1711	$152.17	$152.15	$152.20
Purchase #2	$92.62	4.333%	$96.6332	$96.63	$96.65	$96.60
Purchase #3	$176.47	11.310%	$196.4288	$196.43	$196.45	$196.40
Purchase #4	$107.31	11.744%	$119.9125	$119.91	$119.90	$119.90
Purchase #5	$47.45	12.219%	$53.2479	$53.25	$53.25	$53.20
Purchase #6	$168.59	3.339%	$174.2192	$174.22	$174.20	$174.20
Purchase #7	$199.90	10.524%	$220.9375	$220.94	$220.95	$220.90
7 purchase totals =	$927.82		$1,013.5502	$1,013.55	$1,013.55	$1,013.40