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	$87.92	10.216%	$96.9019	$96.90	$96.90	$96.90
Purchase #2	$221.27	7.740%	$238.3963	$238.40	$238.40	$238.40
Purchase #3	$106.69	8.228%	$115.4685	$115.47	$115.45	$115.50
Purchase #4	$89.70	7.268%	$96.2194	$96.22	$96.20	$96.20
Purchase #5	$82.77	7.850%	$89.2674	$89.27	$89.25	$89.30
Purchase #6	$220.36	10.518%	$243.5375	$243.54	$243.55	$243.50
Purchase #7	$133.97	6.235%	$142.323	$142.32	$142.30	$142.30
7 purchase totals =	$942.68		$1,022.1140	$1,022.12	$1,022.05	$1,022.10