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	$98.84	10.566%	$109.2834	$109.28	$109.30	$109.30
Purchase #2	$34.56	4.117%	$35.9828	$35.98	$36.00	$36.00
Purchase #3	$206.61	7.415%	$221.9301	$221.93	$221.95	$221.90
Purchase #4	$116.46	8.154%	$125.9561	$125.96	$125.95	$126.00
Purchase #5	$95.72	3.665%	$99.2281	$99.23	$99.25	$99.20
Purchase #6	$240.36	11.765%	$268.6384	$268.64	$268.65	$268.60
Purchase #7	$142.82	8.728%	$155.2853	$155.29	$155.30	$155.30
7 purchase totals =	$935.37		$1,016.3042	$1,016.31	$1,016.40	$1,016.30